@AbstractMachine - If you did hand Rob a tenner, my bet is that you'd play the game, or at least try to. You'd mention it to your friends and see if they'd take you up on in. You may not even realize you were doing it.
You're right that money doesn't drive people to play games. What is effective, is to develop a following. The most effective way of doing that is to develop a relationship with people. Message boards help. Having google+ conversations help. Going to cons helps.
But if you cannot meet that person, and they download a game for nothing, there is still no relationship. If they hand you a tenner, now there's a relationship. You have a give and take.
Beyond that there is the perceived value of a thing. If you laid out currency, a little bit of your life, it must be worth something. Why would I expend my money on it otherwise? It must be worth playing.
You might not think that *you* are effected by this kind of thinking, but analyze the games you did play. Walk into a store and pick up a book or a board game. You'll find yourself unconsciously weighing it as a judgement of it's value. There are behaviors that everyone does but no one wants to admit to, or thinks they're exempt from but they're not. Humans are humans. No amount of training yourself will get you to stop thinking like a human.