You can pay a woman to dance. You can pay a woman to be an escort and go out in public. You cannot pay her to have sex but you can have sex with any willing woman in a bar and you can even buy her drinks.
You can pay a minor to provide unlicensed child care in your home in violation of payroll taxes and child labor laws if you call her a babysitter, but you cannot pay a woman to have sex (unless you film it, which costs extra and requires a binding contract or at least a release and proof of age/identity).
The law is a ass.
When "unmarried fornication" was a crime and adultery was a crime, all extramarital sex was a crime whether you paid the participant or not.