this was covered in the 'Freakonomics' book with hookers increasing prices. It's about the girl having the confidence to ask for more and punters willing to pay. She doesn't have to be consistent as any prices offers are one-to-one. So she might try the higher price on 1 in 5 customers and find it works, so then she move to 2/5 etc until she has raised her prices. With the number of reliable high performers available, it's very possible price will go up for the high performers.

but why pay $300 for lousy FS when you can get a brothel experience or a sugarbabe