I dunno chris45, while I agree that deliberate shortchanging is never right, I still think you are way over-reacting.
If Jet has ever done me out of a buck or two, that I hadn't planned on spending, I mustn't have thought it any big deal. Why not just consider it an entertainment cover charge for some entertainment you turned out not to enjoy.
For all you know, he'd just done a bank run, or made special change for someone. Maybe people had been giving him twenties all day. Since another person has piped up and said they also got the gum treatment, it's obviously a learned behaviour that has worked for him in the past.
I could be wrong, but I don't think he's living in a mansion on the hill because of his nefarious ways. Do you really want to potentially put a serious dent in his business just because you had a negative reaction to him?
You are starting to sound like a bully that would try to take a man's livelihood away from him, when you don't necessarily have all the details.
He's a character, not a bad man. Sure, his hotdogs are probably bad, but like Barnacle said . . .