In 2019 the (U.S.) state of Oregon capped hospital prices for state employees at 200% of Medicare costs. A study of 22 hospitals found that there were small but non-significant changes in hospitals' revenues, expenses, and margins as a result, while reducing state expenditures and patients' out-of-pocket costs.
Summary: https://medicalxpress.com/news/2025-12-oregon-nation-hospital-price-cap.html
Original paper (not open access): https://www.healthaffairs.org/doi/10.1377/hlthaff.2025.00682