Most major insurers operate in both the commercial health insurance and Medicare Advantage (MA) markets. We investigated the ratio of commercial-to-MA prices negotiated by the same insurer, in the same hospital and for the same services, using 2022 price information disclosed by hospitals in compliance with the hospital price transparency rule. Insurers negotiated median hospital prices for commercial plans that were two to three times higher than their MA prices in the same hospital for the same service. The median commercial-to-MA price ratio in the same hospital varied, from 1.8 for surgery and medicine services to 2.2 for laboratory tests and emergency department visits and 2.4 for imaging services. In multivariable Poisson regression analysis, higher ratios were associated with system-affiliated, nonprofit, and teaching hospitals, as well as with large national insurers. These findings reflect the differences in financial incentives and regulatory policies in the commercial and MA markets. Because insurers respond to differing incentives by obtaining different negotiated prices across markets, policy and practice efforts that alter incentives for insurers may have the potential to lower commercial prices.