The prices of health care services are a key consideration in the debate over “Medicare for all” and related single-payer proposals. The term prices refers to the allowed payment per unit of service. In the broadest versions of these reforms, in which commercial insurance plans would transition into a universal Medicare–like program, physicians and hospitals face the prospect of receiving Medicare prices for all patients they serve. Relative to the status quo, in which commercial insurer prices generally exceed Medicare prices, this price reduction could have important consequences for clinicians and patients.