Some insight on why a provider may feel inclined to charge more if she offers a shower:
IF she has her own in-call:
Cost of toiletries
Water bill
Cost of towels
Cost of laundry to wash said towels (electricity/water bill, or laundromat costs and washing supplies)
Be that as it may though, it seems like it should be a pretty standard thing during a sesh that the gent will want to shower before and/or after as well. I would also assume if ladies offer such amenities, they work those costs into their rates (that is what I do, but also why I get irritated if people try to low ball my already low rates. Btw gents, I included an assisted shower with every one of my sessions. )
However, as you were at a hotel, that just sounds utterly absurd, as I am sure everything was provided there, including cleaning service.
So yeah, this is just absurd.