I've responded to user requests with "I'm really busy; if you want this to be a priority my rate is $120". Those conversations almost always end with bitching

I've responded to user requests with "I'm really busy; if you want this to be a priority my rate is $120". Those conversations almost always end with bitching (theirs) and me emailing something like "You mistook yourself for a paying customer. You aren't and I still don't work for you. Bye!" then adding their email to my delete on receipt rule.