It's not a direct example, it's a metaphor. They didn't just not pay her. They had sex with her when she didn't want to have sex. She said "no, no. I don't want to have sex. I want to not have sex while a gun is pointed at me" and they said "well, u sell sex so we're just not going to pay!"
You can't walk up to a hooker who you've paid services for before, hold her down, sex her, and then say "This isn't rape, it's stealing." It's rape no matter what her values on sex are, or if she said she'd have sex with you for money.
Please break it down like this: Before money is ever exchanged, they're agreeing to have sex. Ignoring money all together, they're agreeing to have sex. As soon as the sex isn't something she agrees to, she can stop it. If they don't stop, they're raping her. If they paid her after all of this, there'd still be a problem. She was forced to do something she didn't want to do. It wasn't that she was doing something she would later regret, that's not enforceable by law, she made the decision to do it. She did not make the decision to have sex with the partners she did, or while at gunpoint. She made the decision to end it, regardless of the fact of money, and it didn't end.
ᵗʰᵉᵇˢᵍ๒ᵍᵐᵃᶥᶫ∙ᶜᵒᵐ
ᴸᶥᵛᵉ ᴼᵑ ᴬᵈᵃᵐ