It answers it the same way that everyone else has answered it. It doesn't make any sense that you show that you can make money multiply and then take their money. If I saw you do that as a laymen, my first thought would be "Oh, he makes his own money. Good, I don't have to give him mine." Maybe it's just me. I think the best effects to encourage tips are a card to wallet after showing the wallet empty or something using a bill you borrow from them.
Well, from my experience it must be just you. As I mentioned above, my tips are wonderful from performing that trick. In fact, I tested it one night to see how the tips fared against tables that I didn't perform the trick at. Tips were higher at the tables I performed that trick. I still got tips from other tables, but they were larger denominations when I performed the Hundy 500.
As far as showing an empty wallet....that's just basically saying, "Look how poor I am - I don't have any money", which for some people translates to "Look how bad a magician I am - I'm not good enough to make any money so I have to show you my empty wallet in hopes that you will take pity on me and give me a tip."
For my presentation I am showing a fair amount of money (although in the restaurant I work $50 is almost chump change for a lot of the patrons!) which for this clientele translates into a positive, confident, competent character. I carry myself well and project an image that says, "Hey, I'm good and I'm worth every dollar you give me." People in this area like that kind of thing. They like confidence and pay for competent entertainment. It's not cockiness, but confidence in my abilities. I've found through my 10+ years of performing that people like to be fooled. And when you fool them badly from 6 inches away, they appreciate the talent that is involved in pulling that off. I tend to be rewarded fairly well with tips and hourly wages for my talents.