The mechanism: 340B lets hospitals buy outpatient drugs at steep statutory discounts — often 25-50% off list — then bill Medicare, Medicare Advantage, and commercial insurers at full negotiated rates. The spread is legal, unregulated as "profit," and invisible on a hospital's income statement labeled anything but "drug pricing arbitrage." Since HRSA's eligible-site rules are loose, sprawling for-profit systems have quietly built out off-campus outpatient clinics and infusion centers that qualify as 340B "child sites," multiplying the spread across thousands of locations. On June 25, 2026, Senate HELP Chairman Bill Cassidy released a discussion draft — the 340B Drug Pricing Integrity and Affordability for Patients Act — that would tighten eligible-site criteria, mandate a manufacturer rebate alternative, and force patient-level cost-sharing disclosure. Wall Street will cover it as a "drug pricing" headline. It is actually a hospital-margin headline: every eligible site that gets disqualified is a direct cut to pharmacy gross profit at the hospital operator level, not the drugmaker level.