For the past 15 years, a consistent industry argument against low priced generic AIDS drugs in the developing world has been the fear of arbitrage – poor people selling their drugs, undercutting drug company profits. Great soundbite; zero empirical evidence that it ever happens. Nice economic theory, but we still have no evidence of any commercial scale diversion of AIDS drugs from developing countries to rich countries. Zero. (Background: Pharmaceutical Arbitrage)*
And yet, this question is being raised again, this time with the newly approved Truvada preventative treatment for HIV.
Meanwhile, back in the US, a single ring in NYC has allegedly diverted over $100 million in such drugs over the past few years. The WSJ reports on the indictments. US drug prices are so high that they approach cocaine on a per ounce basis. No wonder this entirely domestic trade exists. But that is not an argument for denying low priced drugs to desperately poor people who depend on these drugs for daily life.
*If your response in the comments is to mention the Dowelhurst diversion reported a decade ago (Guardian story here), note that the drugs were diverted in Europe, not Africa. Additional details in Health Affairs 2008 (at n.49-51).