The tour card idea is great!!! I like it.
They could even charge a fee for it, but increase the purses of the Tour Champion tier to something > Champ by quite a bit. Not crazy large, but enough to make people want to buy that tour card in order to play for the largest purses.
Or, have a qualifying tourney -- which you pay for and if you qualify your reward is you get to play for tourney's with the highest purses available. Do well, and you won't spend a dime (Like on the real tour), but struggle and it'll become a grind where you'll have to decide if it's worth the $$$ to get there.