A study of autoworker claims found that hospitals with the highest prices tended to have the strongest reputations and tight holds on their local markets yet showed little evidence of providing better quality care. The actual prices insurers pay hospitals are closely guarded secrets in health care. That has made it hard for health researchers to study one of the most important issues: whether patients get better treatments from more expensive hospitals. Hospital list prices, which Medicare published last year, provide no indication about how much hospitals actually are compensated by private insurers.