In a remarkable paper, Andrew Francis (a graduate student at the University of Chicago) examines how AIDS has changed sexual choice. With admirable precision, Francis lays out the price of sex:
...it is thousands of times more likely that a male would get HIV having sex with a man than having sex with a woman. In terms of AIDS-related mortality, the expected cost of having unprotected sex once with a man is almost $2000, while the expected cost of having unprotected sex once with a woman is less than a dollar.