You'll have to check current prices to be sure, but I would expect a .22 or .25 In the Lorcin, Jennings, Bryco, Raven, etc. class would be it.
I don't follow the MSRP pricing on these kinds of things, but I do recall that before the Obama fear cycle set in, they were selling for $60-75 brand new. I think today they are in the $100-120 range.
Good luck, and let us know who wins the bet!
Also, as the guy who thinks its foolish to spend more than $200 on a handgun what he thinks is foolish to spend on tires, something else he bets his life on, and much more often.