My WW assured me that her cheating was not about the sex.
"Then why was there sex?", I wondered.
Short version of the answer: It was clear he wanted sex, and she wanted the relationship to continue. She wanted the attention, the compliments, the flirting.
She traded sex for that.
A common definition of "prostitution" is "providing sexual favors for compensation."
The compensation can take any form: money, gifts, a role in a movie, etc.
Or attention, compliments, flirting.
Maybe this is what OP is talking about.
(And while I’m talking about my WW, the same applies to cheating men. There are gigolos in the world, I suppose.)