Well you haven't paid a dime in NASA funding yet. All funding to date has been borrowed from people younger than you or not yet born. Presumably the gov't will borrow many times more to get to Mars, than it has for any previous mission.
If the US wasn't $17 trillion in debt, I could agree. Pretty sure all NASA funding to date fits into that debt amount. Since it's a "nice to have", I'd say the average taxpayer has never paid anything to NASA, not even interest on debt since we borrow to pay that.
