1. For one, they suggest that only at-risk men engage in pre-exposure prophylaxis, or PrEP — those who have five or more sexual partners a year. If 20% of those people took the pill, that would lead to a drop of 41,000 cases for a cost of $16.6 billion. That’s a bill of $1,185,714.29 per case, which seems still rather a lot of money, but apparently amounts to “$50,000 per quality-adjusted life year gained (a measure of how long people live and their quality of life)”