For decades, the prices that hospitals and physicians charge private insurers have been treated as trade secrets. Even though inflated prices are an enormous reason why health care is so much more expensive in the United States than in other countries, we have only a hazy picture of what those prices actually are.
Bagley, Nicholas and Christopher Koller. "Transparency and the Supreme Court—Can Employers Refuse to Disclose How Much They Pay for Health Care?" New England Journal of Medicine 373 (2015): 1-3.