Budgeting is an important part of a college education. But try to factor this into monthly expenses: prescription contraceptives that cost $10 for last month’s supply will now cost $50.

For almost 20 years, college health centers could buy prescription drugs, including contraceptives, at an extraordinary discount of some 90 percent. This arrangement was not a subsidy and did not cost taxpayers a dime. Rather, to encourage the pharmaceutical companies to be generous to certain charitable groups, Congress gave the manufacturers a limited exemption from Medicaid pricing rules.

All was well until accusations arose that some drug companies were abusing the exemption — trading those big discounts for product promotion in hospitals, for example. Congress narrowed the definition of those who could qualify and unintentionally excluded university health centers and some clinics that serve low-income women. The tighter definitions went into effect in January. Many clinics stockpiled contraceptives, but reserves are starting to run out, and prices are shooting up.

Generics are a cheaper option, but still more expensive than many brand-name contraceptives bought under the old system. Generics are also not available for many newer products, some of which use lower hormone levels or do not require women to take a daily dose.

Representative Joseph Crowley, Democrat of New York, has introduced a sensible measure that would make university health centers and safety-net clinics eligible for the discount again. Last week, Senators Barack Obama, Democrat of Illinois, and Claire McCaskill, Democrat of Missouri, unveiled a similar bill. The legislation deserves swift passage. College students and low-income women should not be priced out of family planning.