CMS now requires hospitals to publish machine-readable price files under the Hospital Price Transparency Rule (effective 2021, enforcement added 2022). Compliance rates are technically high. The problem is the files run tens of thousands of line items in inconsistent formats, negotiated rates vary by insurance plan, and chargemaster list prices bear no predictable relationship to what any patient actually pays.

RAND's Round 5.1 study analyzed actual paid claims rather than posted prices and found commercial insurers paid 254% of Medicare rates for identical procedures at the same hospitals. The transparency is on paper. The opacity is structural: a price list is only useful if a purchaser can act on it, and the moment of care is not when most patients can comparison shop. Which is why reference pricing works at the employer level (purchaser can act in advance on a population basis) but published hospital price lists have not moved the market.