The price of gamemaking for the Xbox Live Marketplace

Seems like producing games for the Xbox Live Marketplace might be a good way to make a pretty penny. GarageGames co-founder Jeff Tunnell gives it to us straight on what it could costs and how much you could profit from making a game and releasing it on the Xbox Live Market place. From what he says, it looks like actually making the game will run you around $100,000 to $300,000 and if you game gets popular, you could end up making close to a million. What I would be interested is in how long would money continue to roll in for these top games. Would the whole long tail theory of content being viable over the long term apply here? Time would tell for sure.