 Medallions, or CPNC (Certificate of Public Necessity and Convenience), may also be sold in Boston, or Chicago, but in San Francisco—one of the few other cities that has medallions—the sale of medallions became prohibited by Prop K in 1978.This proposition was adopted to stop speculators from driving the price of medallions up beyond the reach of the people who provide the service—the drivers.In 2010, the City of San Francisco attempted to allow the sale of medallions (for an estimated $250,000 each) in order to balance the City budget.