How do we assign a value to goods and services? Money is the answer. This is why money was invented. It's hard to barter something YOU think has a certain value which I think is worth a different value.
EXAMPLES:
*** A client wants me to meet him at the Galleria and we will spend my fee on sexy corsets and garter belts together and then go back to my incall for playtime to repay him for that fee.
PROBLEM: That's not how I was going to spend my fee. He doesn't get to dictate how the money is spent when he is paying me.
SOLUTION: He can come to my incall, have our date, and then pay me and watch me do online bill payment with it if he finds it fun to spend MY money together. Because that's how I intend to spend the money I make today. LOL!
***A client is dying to eat at a very pricey restaurant where multiple courses will cost hundreds of dollars. Is it ok if he pays for the meal in lieu of my fee?
PROBLEM: Same as above, that's not how I would have spent **MY*** money. If you're going to pay me a fee, then YOU don't get to decide how I spend MY fee

SOLUTION: He can spend his own money to eat at the fancy place alone and them come visit me and pay me my fee in cash, equivalent to what he was going to spend for my meal. I'll eat simply on my own dime and have more money left to pay my bills.
***A hobbyist recently asked if airfare, hotel costs, and meals are enough to compensate an escort for a long weekend out of state.
PROBLEM: If she wants to spend HER money (the fees she collects), then she gets to pick the flight/hotel/destination/and her traveling companions ( a sister, a friend, a fellow provider, kids)/ and have independence.
SOLUTION: Waiting to see how this gets solved. Probably a local lady out there will be best since she doesn't NEED the airfare/hotel/meals and can give him the actual cost in dollars for her time.