That's not the issue from the incel perspective. Essentially, why should they 'stoop' to that level, as only real losers will pay for sex, and sure, it'll feel great, but you'll feel crap again straight after.
Remember as well, they'll feel they
deserve sex, they're
entitled to sex, that they're
owed sex. And not just from anyone, but from the most beautiful females out there. 'Ugly' girls simply won't do, and they won't 'stoop' or 'settle' for that because they're far better than that. And of course, when the girl (and often, 'the girl' is an abstract concept, because they'll often have zero actual experience of relating to, conversing with, socialising with, interacting with actual females) 'rejects' them, and again, I use this term loosely, because 'the girl' might be completely unaware of this whole thing, and is just going about her day (and this is still rejection) - literally, her not showing any interest, or her not just magically falling onto their penises in sheer awe and despair at their sheer magnificence, it's her problem. She is to blame. It's her fault. She is the one wronging the poor incel, and she deserves to be punished.
It's a sickening, and skewed perspective.