^ Basically what he said.

Plus, for drugs:
Supply & Demand » since illegal, there's low supply » prices go up.
Interestingly, most drug dealers already have criminal convictions, so their potential "loss" of supplying drugs is lower.

Prostitution pretty much follows the above » since it's considered "bad" by society, not many people are willing to enter the market.  If every 5th girl was a prostitute, expect the prices to go down a fair bit...
(also interestingly, most girls who enter the market are probably school drop-outs)

(This post was last modified: 28/06/2008 04:09 AM by ZiNgA BuRgA.)