NPR's excellent health blog has a great discussion about Truvada, the HIV retroviral that the FDA just approved as a preventive treatment for a specific sub group of HIV patients: http://www.npr.org/blogs/health/2012/07/17/156868446/deciding-on-truvada-who-should-take-new-hiv-prevention-pill?ps=sh_stcathdl
The debate about the cost is a false one. At a retail price of $13k a year, Truvada is a bargain compared to what we lose and what we spend on treating HIV.
My bet is that insurers will pay for this targeted preventive treatment. As Mark Duggan has shown: previous HIV treatments have reduce Medicaid spending by 16 percent and increase life expectancy by a factor of three.