I think we all "know" what prostitution is, or do we? You are in a hotel and go to the bar, see a hooker and hire her for sex, prostitution. You are in a hotel and go to the bar, see a woman, buy her a drink, take her to dinner, then to your room and have sex, not prostitution.
So where is the line crossed? Asking? Talking about it? Cash instead of drinks and a dinner? Someone knowing her occupation? Has to be something...


Direct payment for sex = prostitution
Gratuities not obliging the recipient to repay with sexual favors = not prostitution, but consensual activity