The more than $35,000 annually that Ms. Yapalater and her employer collectively pay in premiums — her share is $15,000 — for her family’s Oxford Freedom Plan would be more than sufficient to cover their medical needs in most other countries. She and her husband, Jeff, 63, a sales and marketing consultant, have three children in their 20s with good jobs. Everyone in the family exercises, and none has had a serious illness.

Like the Yapalaters, many other Americans have habits or traits that arguably could put the nation at the low end of the medical cost spectrum. Patients in the United States make fewer doctors’ visits and have fewer hospital stays than citizens of many other developed countries, according to the Commonwealth Fund report. People in Japan get more CT scans. People in Germany, Switzerland and Britain have more frequent hip replacements. The American population is younger and has fewer smokers than those in most other developed countries. Pushing costs in the other direction, though, is that the United States has relatively high rates of obesity and limited access to routine care for the poor.

A major factor behind the high costs is that the United States, unique among industrialized nations, does not generally regulate or intervene in medical pricing, aside from setting payment rates for Medicare and Medicaid, the government programs for older people and the poor. Many other countries deliver health care on a private fee-for-service basis, as does much of the American health care system, but they set rates as if health care were a public utility or negotiate fees with providers and insurers nationwide, for example.

“In the U.S., we like to consider health care a free market,” said Dr. David Blumenthal, president of the Commonwealth Fund and a former adviser to President Obama. ”But it is a very weird market, riddled with market failures.”

Consider this:

Consumers, the patients, do not see prices until after a service is provided, if they see them at all. And there is little quality data on hospitals and doctors to help determine good value, aside from surveys conducted by popular Web sites and magazines. Patients with insurance pay a tiny fraction of the bill, providing scant disincentive for spending.

Even doctors often do not know the costs of the tests and procedures they prescribe. When Dr. Michael Collins, an internist in East Hartford, Conn., called the hospital that he is affiliated with to price lab tests and a colonoscopy, he could not get an answer. “It’s impossible for me to think about cost,” he said. “If you go to the supermarket and there are no prices, how can you make intelligent decisions?”

Instead, payments are often determined in countless negotiations between a doctor, hospital or pharmacy, and an insurer, with the result often depending on their relative negotiating power. Insurers have limited incentive to bargain forcefully, since they can raise premiums to cover costs.