Only going from what I have read around, since the ladies are considered independent contractors really, they can charge what they want for services offered. However I have read that some establishments do make you put down a deposit if you make an appointment. I guess that is to possibly cover them in case a party doesn’t happen? But that I think is the decision of the establishment.
However I am sure that you could negotiate for that kind of party. And if you can’t maybe step away and talk with someone else.
Recently read something from someone saying that they were pressured into a party when they visited Sheri’s I think it was and was thinking, well, unless they threatened you or something, you can always walk away.