yeah my advice would be if you want to get laid a lot in asia for cheap, better go to thailand or philippines. u can get there a beauty for only $ 100 all night. $25 a ugly whore. in japan, prices for sex are extremely higher, but i think no where else u will find a sex market like in japan, u can go to kabukicho in shinjuku and u will find a girl from almost every country in the world: russians, koreans, even american prostitutes, etc. and u can go into every sex area, costume, masochism, pregnant, teenagers, anime, etc but well some will even try to charge you $300 for only one hour, which is a big difference and if you want a really japanese beauty, well prepare $500 or more.
yokohama has a red district that is very small but where u can get laid for 100 dollars. but most of the girls there are chinese and koreans.
of course, if you have good attitude and playboy skills, the cheapest and easiest is to go to ropongi and try to pick up a girl for free as everyone does...