Prescription drugs are considerably more expensive in the US than in other countries. As a result, millions of people are unable to afford important, often lifesaving medicines. In this issue of JAMA Internal Medicine, Haque et al1 demonstrate the higher prices for humans than for pets in the US for the same generic drug. Their study raises a fundamental question: how large a margin between production costs (including the costs of research and manufacturing) and sales price is acceptable for prescription drugs?