If you want to be completely tactless, the best way to approach it is to just say any old thing that pops in your head (without thinking about it first of course). Make sure that you say it in a tone of voice (intentionally or not) that exudes a “mocking” feeling and that it’s directed towards someone from whom you want money.
Personal experience. We have a problem at the place where I work. We have disappearing pen syndrome. Historically, I would have to refill the pen jar only once a day, but more recently, a black hole has developed in the bottom of the jar. Either that or we have pen stealing elves. Seriously, I put 3 or 4 new pens in, and 10 minutes later, they’re gone! I now know the reason people tape flowers or forks or bar codes on their pens so they don’t disappear so readily. We don’t have any bar codes, but I’ve been thinking about taping a chair to the pen. Maybe then, we could catch the elves before they escape in victory.
Anyway, so yesterday, a customer came in, ordered some things, borrowed a pen to sign a receipt, and started walking out the door. She stopped, and turned around to return the pen. As she did, I said, “Thanks for not stealing our pen!” I didn’t think it was that bad, but all my coworkers were turning red from holding in the laughter, and she looked at me as if I had said, “your wig is falling off and I hate your mother.” That's the way it goes I guess. Just another day in the life of almost Marylund.