This year, the federal government ordered hospitals to begin publishing a prized secret: a complete list of the prices they negotiate with private insurers.

The insurers’ trade association had called the rule unconstitutional and said it would “undermine competitive negotiations.” Four hospital associations jointly sued the government to block it, and appealed when they lost.

They lost again, and seven months later, many hospitals are simply ignoring the requirement and posting nothing.

But data from the hospitals that have complied hints at why the powerful industries wanted this information to remain hidden.

It shows hospitals are charging patients wildly different amounts for the same basic services: procedures as simple as an X-ray or a pregnancy test.

And it provides numerous examples of major health insurers — some of the world’s largest companies, with billions in annual profits — negotiating surprisingly unfavorable rates for their customers. In many cases, insured patients are getting prices that are higher than they would if they pretended to have no coverage at all.

Until now, consumers had no way to know before they got the bill what prices they and their insurers would be paying. Some insurance companies have refused to provide the information when asked by patients and the employers that hired the companies to provide coverage.

This secrecy has allowed hospitals to tell patients that they are getting “steep” discounts, while still charging them many times what a public program like Medicare is willing to pay.

And it has left insurers with little incentive to negotiate well.

The peculiar economics of health insurance also help keep prices high.

How to look up prices at your hospital (if they’re there) ›

Customers judge insurance plans based on whether their preferred doctors and hospitals are covered, making it hard for an insurer to walk away from a bad deal. The insurer also may not have a strong motivation to, given that the more that is spent on care, the more an insurance company can earn.

Federal regulations limit insurers’ profits to a percentage of the amount they spend on care. And in some plans involving large employers, insurers are not even using their own money. The employers pay the medical bills, and give insurers a cut of the costs in exchange for administering the plan.

A growing number of patients have reason to care when their insurer negotiates a bad deal. More Americans than ever are enrolled in high-deductible plans that leave them responsible for thousands of dollars in costs before coverage kicks in.

Patients often struggle to afford those bills. Sixteen percent of insured families currently have medical debt, with a median amount of $2,000.

Even when workers reach their deductible, they may have to pay a percentage of the cost. And in the long run, the high prices trickle down in the form of higher premiums, which across the nation are rising every year.

Insurers and hospitals say that looking at a handful of services doesn’t provide a full picture of their negotiations, and that the published data files don’t account for important aspects of their contracts, like bonuses for providing high-quality care.

“
These rate sheets are not helpful to anyone,” said Molly Smith, vice president for public policy at the American Hospital Association. “It’s really hard to say that when a lot of hospitals are putting in a lot of effort to comply with the rule, but I would set them aside and avoid them.”

The trade association for insurers said it was “an anomaly” that some insured patients got worse prices than those paying cash.

“
Insurers want to make sure they are negotiating the best deals they can for their members, to make sure their products have competitive premiums,” said Matt Eyles, chief executive of America’s Health Insurance Plans.

The five largest insurers — Aetna, Cigna, Humana, United and the Blue Cross Blue Shield Association — all declined requests for on-the-record interviews. Cigna, Humana and Blue Cross provided statements that said they support price transparency.

The requirement to publish prices is a rare bipartisan effort: a Trump-era initiative that the Biden administration supports. But the data has been difficult to draw meaning from, especially for consumers.

The New York Times partnered with two University of Maryland-Baltimore County researchers, Morgan Henderson and Morgane Mouslim, to turn the files into a database that showed how much basic medical care costs at 60 major hospitals.

The data doesn’t yet show any insurer always getting the best or worst prices. Small health plans with seemingly little leverage are sometimes out-negotiating the five insurers that dominate the U.S. market. And a single insurer can have a half-dozen different prices within the same facility, based on which plan was chosen at open enrollment, and whether it was bought as an individual or through work.

But the disclosures already upend the basic math that employers and customers have been using when they try to get a good deal.

People carefully weighing two plans — choosing a higher monthly cost or a larger deductible — have no idea that they may also be picking a much worse price when they later need care.

Even for simple procedures, the difference can be thousands of dollars, enough to erase any potential savings.

It’s not as if employers can share that information at open enrollment: They generally don’t know either.

“
It’s not just individual patients who are in the dark,” said Martin Gaynor, a Carnegie Mellon economist who studies health pricing. “Employers are in the dark. Governments are in the dark. It’s just astonishing how deeply ignorant we are about these prices.”

A vital drug, a secret price

Take the problem Caroline Eichelberger faced after a stray dog bit her son Nathan at a Utah campsite last July.

Nathan’s pediatrician examined the wound and found it wasn’t serious. But within a week, Nathan needed a shot to prevent rabies that was available only in emergency rooms.

Ms. Eichelberger took Nathan to Layton Hospital in Layton, Utah, near her house. It hasn’t published price data for an emergency rabies vaccine, but the largest hospital in the same health system, Intermountain Medical Center, has.

Nathan, then 7 years old, received a child’s dose of two drugs to prevent rabies. The bill also included two drug administration fees and a charge for using the emergency room.

Intermountain owns a regional insurer called SelectHealth. It is currently paying the lowest price for those services: $1,284.

In the same emergency room, Regence BlueCross BlueShield pays $3,457.

Ms. Eichelberger’s insurer, Cigna, pays the most: $4,198.

For patients who pay cash, the charge is $3,704. Half of the insurers at Intermountain are paying rates higher than the “cash price” paid by people who either don’t have or aren’t using insurance.

This pattern occurs at other hospitals, sometimes with more drastic consequences for adults, who require a higher dosage.

Prices were still secret when Brian Daugherty went to an emergency room near Orlando, Fla., for a rabies shot after a cat bite last summer.

“
I tried to get some pricing information, but they made it seem like such a rare thing they couldn’t figure out for me,” he said.

He went to AdventHealth Orlando because it was close to his house. That was an expensive decision: It has the highest price for rabies shots among 24 hospitals that included the service in their newly released data sets.

The price there for an adult dose of the drug that prevents rabies varies from $16,953 to $37,214 — not including the emergency-room fee that typically goes with it.

Mr. Daugherty’s total bill was $18,357. After his insurer’s contribution, he owed $6,351.

“
It was a total shock when I saw they wanted me to pay that much,” said Mr. Daugherty, who ultimately negotiated the bill down to $1,692.

In a statement, AdventHealth said it was working to make “consumer charges more consistent and predictable.”

If Mr. Daugherty had driven two hours to the University of Florida’s flagship hospital, the total price — between him and his insurer — would have been about half as much.

Similar disparities show up across all sorts of basic care.

One way to look at the costs is to compare them with rates paid by Medicare, the government program that covers older people. In general, Medicare covers 87 percent of the cost of care, according to hospital association estimates.

At multiple hospitals, major health plans pay more than four times the Medicare rate for a routine colonoscopy.

And for an M.R.I. scan, some are paying more than 10 times what the federal government is willing to pay.

Health economists think of insurers as essentially buying in bulk, using their large membership to get better deals. Some were startled to see numerous instances in which insurers pay more than the cash rate.

Whether those cash rates are available to insured patients varies from hospital to hospital, and even when they are, those payments wouldn’t count toward a patient’s deductible. But the fact that insurers are paying more than them raises questions about how well they’re negotiating, experts said.

“
The worrying thing is that the third party you’re paying to negotiate on your behalf isn’t doing as well as you would on your own,” said Zack Cooper, an economist at Yale who studies health care pricing.

‘

They don’t want their secrets out there’

Employers are the largest purchasers of health insurance and would benefit the most from lower prices. But most select plans without knowing what they and their workers will pay.

To find out what the prices are, they would need to solicit bids for a new plan, which can frustrate employees who don’t want to switch providers.

It also requires the employers to hire lawyers and consultants, at a cost of about $50,000, estimated Nathan Cooper, who manages health benefits for a union chapter that represents Colorado sheet metal and air-conditioning workers.

“
If you want the prices, you have to spend to get them,” he said.

Employers who do sometimes come up empty-handed.

Larimer County, in Colorado, covers 3,500 workers and their families in its health plan. In 2018, county officials asked their insurer to share its negotiated rates. It refused.

“
We pushed the issue all the way to the C.E.O. level,” said Jennifer Whitener, the county’s human resources director. “They said it was confidential.”

Ms. Whitener, who previously managed employer insurance contracts for a major health insurer, decided to rebid the contract. She put out a request for new proposals that included a question about insurers’ rates at local hospitals.

A half dozen insurers placed bids on the contract. All but one skipped the question entirely.

“
They don’t want their secrets out there,” Ms. Whitener said. “They want to be able to tout that they’ve got the best deal in town, even if they don’t.”

Hospitals and insurers can also hide behind the contracts they’ve signed, which often prohibit them from revealing their rates.

“
We had gag orders in all our contracts,” said Richard Stephenson, who worked for the Blue Cross Blue Shield Association from 2006 until 2017 and now runs a medical price transparency start-up, Redu Health. (The association says those clauses have become less common.)

Mr. Stephenson oversaw a team that made sure the gag orders were being followed. He said he thought insurers were “scared to death” that if the data came out, angry hospitals or doctors might leave their networks.

Warnings, but no fines

Ms. Eichelberger’s plan had a $3,500 deductible, so she worked hard to find the best price for her son’s care.

But neither the hospitals she called nor her insurer would give her answers.

She made her decision based on the little information she could get: a hospital, Layton, that said it would charge her $787 if she paid cash. The price for paying with insurance wouldn’t be available for another week or two, she was told.

But even the cash price didn’t turn out to be right: A few weeks after the visit, the hospital billed her an additional $2,260.

It turns out that the original estimate left out a drug her son would need.

“
It was the most convoluted, useless process,” said Ms. Eichelberger, who was able to get the bill waived after five months of negotiations with the hospital.

Daron Cowley, a spokesman for Layton’s health system, Intermountain, said Ms. Eichelberger received the additional bill because “a new employee provided incomplete information with a price estimate that was not accurate.”

The health system declined to comment on prices at its hospitals, saying its contracts with insurers forbid discussing negotiations.

It’s not clear how much better the Eichelbergers would do today.

The new price data is often published in hard-to-use formats designed for data scientists and professional researchers. Many are larger than the full text of the Encyclopaedia Britannica.

And most hospitals haven’t posted all of it. The potential penalty from the federal government is minimal, with a maximum of $109,500 per year. Big hospitals make tens of thousands of times as much as that; N.Y.U. Langone, a system of five inpatient hospitals that have not complied, reported $5 billion in revenue in 2019, according to its tax forms.

As of July, the Centers for Medicare and Medicaid Services had sent nearly 170 warning letters to noncompliant hospitals but had not yet levied any fines.

Catherine Howden, a spokeswoman for the agency, said it expected “hospitals to comply with these legal requirements, and will enforce these rules.”

She added that hospitals that do not post prices within 90 days of a warning letter “may be sent a second warning letter.”

The agency plans to increase the fines next year to as much as $2 million annually for large hospitals, it announced in July.

The hospital that treated Ms. Eichelberger’s son has begun posting some information. But it has spread its prices across 269 web pages. To look for rabies, you have to check them all. It isn’t there.