It might still be taboo in some quarters, but I think you underestimate the deterrent effect that legal risk has. It's really easy for a girl to operate discretely, maintaining a separate life and deniability, if she chooses to do so, especially in the Metroplex, where she could easily live in one city and work in another. But I think a lot of women are deathly terrified of having to answer for a prostitution arrest to friends and family, and coworkers and bosses, current or future.
Removing the need for women to charge a risk premium for their legal risk would increase the supply, and lower prices would follow. What you would probably see would be a lot more part-timers: students, women with full-time jobs meeting for an hour after work, women with part-time jobs. I'll bet you'd also see a decrease in the number of girls making six figures.
That's what I thought until I looked at Colorado law. Green stuff is more expensive since they can tax it.
We need to make a distinction between legalizing it and decriminalizing it. Legalization would subject it to regulation and taxation, and would indeed adversely affect the price. Merely removing of criminal sanctions would simply eliminate legal risk, and the need to charge a premium for it.