I was about ready to make the same case, until I went to research it and found that in 2007, a Philadelphia judge ruled that a woman that agreed to sex with 2 men for $250, then was forced to have sex with them for free at gunpoint, was not a rape victim, but that the men had committed "Theft of Services".
Fortunately, the bar later rebuked her for the classification. It was a little more difficult to find further precedent, since I'm doing it on my phone at work, and I don't really need "If you don't pay a prostitute, is it rape?" or some variant thereof in my work computer's search history.