[ZachPruckowski]

You can, it's just really hard.

This is basically what Minecraft is doing - the game is entertaining now, but it's also got INSANE potential. So it's absolutely worth plopping $13 down on. Notch made $3 million or whatever (enough to fund game development) on the alpha sales. Of course, he may have trouble making money post-release if he can't charge the people who bought Alpha for the full version and if most of his potential audience buy Alpha or Beta.

Torchlight had the right idea, I think - create a fun initial product, and use the income from that to fund your more expensive V 2.0 that has a subscription model.