Ordinary U.S. residents have a hard time imagining how much prices for medical services vary in this country.

Researchers at HealthMarkets Inc., North Richland Hills, Texas, have published figures supporting that conclusion in a summary of results from a November telephone survey of 1,028 U.S. residents ages 18 and older living in private households in the United States.

HealthMarkets recently acquired the old HealthMarket Inc., a Connecticut startup that helped introduce the idea that health insurers should inform plan members what care from specific doctors actually costs.

Despite all of the attention now being paid to “health care price transparency,” only 23% of the survey participants said they believed they knew a “great deal” or “some amount” about how the prices their doctors charge compare to what other doctors charge for the same procedure, HealthMarkets researchers report.

Moreover, when survey interviewers asked participants about cost variation for typical procedures, the participants had a tough time guessing how much greater the maximum U.S. price might be than the lowest price, researchers report.

The interviewers noted, for example, that the lowest price for a CT scan of the abdomen costs $298. When the interviewers then asked what they thought the maximum charge for the procedure would be, 73% of participants said the maximum would be $2,000 or less.

In reality, HealthMarkets pricing figures show some doctors charge about $3,000 for abdominal CT scans, the researchers write.

Similarly, when told that a tonsillectomy costs $2,300, 75% guessed the highest price a doctor would charge would be $9,000 or less, but some doctors charge $13,000 for tonsillectomies, the researchers report.