The following comment from the BBC's talking point Condoms and culture: Ask the experts has made me wondered if Japan's rampant sex trade had anything to do with gender role (namely that the men get the high salaries, while women serve tea or just stay at home).

Sex in Africa for most women is regarded as a source for material gains (including sex in return for food). As long as we do not fight poverty, Aids will continue decimating the sub-Saharan people.
It seems to me that most Japanese girls who are in the "sex trade" (be it direct prostitution, enjo kosai, or just pornography, tere-kura, hostess bar or selling their used panties to perverts...) all want to get a lot of money in exchange for sexually related services. I could thus change the above sentence by : Sex in Japan for most women is regarded as a source for material gains (including sex in return for brand clothes, handbags, trips to hot springs and expensive restaurants).

As long as women don't have the same work opportunity as men in culture so open to sex as Japan (read non Judeo-Christo-Islamic), (good-looking) women will continue to take advantage of their body to make easy money. The worst is that even if perfect gender equality is achieved, as long as mentalities regarding sex and the risk of STD's don't evolve, Japanese (and other East Asian) women will have no scrupule to do make money from their feminity.