alot of pornstars these days are in the prostitution business, there are a few major websites that are pornstar prostitution portals - the funniest thing the whole activity has become known as a 'hobby' , no doubt the guys who do this alot trying to save a little dignity by making it sound no more unusual than a guy who is into model railroading.
http://www.bigdoggie.net
The Erotic Review is another.
I think prices vary alot depending on which girl and the situation.
In the old days girls went into adult movies to build up their name so they could hit the feature dancer circuit and make the big money which adult movies don't pay. These days girls are in adult movies to promote their whoring careers.
Pornstars do alot of this whore work when they are on the dance circuit.