Restrictionists point to the so-called "pill mills" rampant in the earlier years of this century, particularly in South Florida, and the Appalachian region, that churned out hundreds of millions of prescription painkillers. The pill mills weren't indicative of how the overwhelming majority of doctors practice pain management.
While they are largely gone now, pill mills are an example of what happens when drug prohibition intersects with the third-party payment system.
Drug prohibition creates lucrative black market opportunities for people willing to sell drugs illegally. In 2011 federal law enforcement reported the street price of OxyContin was $50 to $100, compared to the legal price of roughly $6 at the pharmacy. In fact, when Florida clamped down on its pill mills the street price of a single OxyContin pill rose from $8 to $15.