I can't even wrap my head around how OP is considering a model S for a teenagers first car. The cost to buy and maintain the car isn't part of the issue at all for me, cause maybe OP is ballin and has no problem throwing down that sort of cash for stuff. What gets me is what's already been said here several times -- but I'll say it again anyway -- a model s is far too much car for a teen to learn on. Will OP's kid kill himself with it? Maybe not but I think an S invites far more stupid ass decisions on the kid's part vs a 500e/Versa/Prius would. At the end of the day, buy him what makes sense.
Oh and I agree, you shoulda beat him for thumbing his nose up at an mr2!