To be honest, I don't think rates would just drop randomly. It would be dictated by the market just like other commodities; your top rated gals (or guys) would still be charging top dollars.
There have been other regulation systems in the past where it was "successful" for the most part (ancient Rome, during the American Civil war, etc...), at the very least the providers were safe (physically, medically and criminally - can't speak for how they were viewed socially).
I personally do not like the labeling of sex workers in general (mostly negative) which degrades them, it feel like we as people need to put others down to make ourselves feel better (if a person is truly great, there is no need to advertise or compare). I think we should start with changing that mindset first before any change can happen (pipe dream, I know).