A good point to note is how hard the individual girls work for that money. Considering the turnover of those girls in that industry - anything over 29, and they're usually considered over the hill, and at 35 you can stick a fork in them, they're done - they are driven to seek out the customers who will pay them the maximum amount of money in the shortest period of time, because that window of time is very short indeed.
It's a business that demands maximum efficiency. No fat. All lean meat. Physically, as well as metaphorically. A lesson for us all.