Part of Yale's online course Understanding Medical Research: Your Facebook Friend is Wrong, this lecture explains how researchers and health economists measure whether a medical treatment is worth its price. The instructor walks through cost-effectiveness analysis, including how outcomes are converted into comparable units such as quality-adjusted life years, and why a drug or procedure that works can still fail a cost-effectiveness test if cheaper alternatives produce nearly the same benefit. Examples show how these calculations shape decisions by insurers, hospitals, and health systems about which treatments to cover. The lecture is aimed at a general audience trying to read medical news critically, so it keeps the math simple and focuses on the logic of comparing costs to benefits rather than technical statistical methods.