When I'm COMPELLED, I tip like Rockefeller... otherwise I align with Ms. Post.
If your fee is $400 or higher, I anticipate 'compelled' and that the tip is already builtin.
250$ seems to be a new standard for some massage providers. Their vague description seems to be code for 'I'll decide when I see what you look like.' But it certainly doesn't get to the escort service.
I know that visiting providers are busy but making certain that you're clean and fresh for your next guest is essential (for my tastes anyhow.). The other reason is, perhaps, subjectives so I'll leave it there.