The legalization of cannabis and the arrival of nonmedical fentanyl are fundamentally changing drug markets in North America. A large part of these changes relates to the ability to produce large quantities of the drugs at low costs, which has slashed wholesale prices for both drugs and retail prices for cannabis. A new analysis explores the effects of these changes on use. The analysis concludes that sharp declines in production costs for cannabis and opioids could dramatically reduce the price per dose for consumers in ways that alter patterns of use and dependence.