Well, you wouldn't buy Pokemon, Yu-Gi-Oh, Magic: The Gathering cards if you hadn't at least spent some time playing. Those are games which have had, at least at some point in their lifespan, large communities of players. I kinda doubt rich people are randomly buying mint alpha Black Lotus cards with no knowledge of the game?

Side note: you can still fail with this type of monetization even if the game is huge (see: Diablo 3 auction house). Once you screw up the economy or drive away the player base, it's hard to recover.