I hit on a mention on another blog of a forthcoming paper by Steven Levitt (of Freakonomics fame) and Sudir Venkatesh (familiar to Freakonomics readers as the crazy Indian guy who went into the projects in Chicago to study the street level economics of the drug trade. This piece (yet to be published, but a preliminary copy is available here as a PDF) is about the economics of street prostitutes in Chicago.
Perhaps the most interesting result: there is a lot more crooked officer stuff going on than expected (or at least than I had expected. They figure that roughly 3% of all tricks turned by the average street hooker were freebies demanded by police in order to avoid arrest!
Also interesting (and counter to what everyone else would have assumed): having a pimp is worth it! The girls with pimps had higher per-hour wage equivalents, even after subtracting out the pimp's take.