Cliffy B from Epic games has gone on record to say that in his opinion all games should be 20 bucks at launch. The reasoning behind that is that most people don't even question blowing 20 bones on DVDs and that they could really capture the "impulse-buy" market at that price point. Think about it, if a game came out that you had been looking forward to, you wouldn't think twice about dropping 20 bucks on it at release. At 50 dollars you may wait for a review, and if it comes in a bit lower than you think it should have, you may pass on the game and put that 50 dollars somwhere else.
Hopefully Cliffy can convince the powers that be because I think that he's absolutely right, and I would gladly buy pretty much any game that tickles my fancy on day one if it launched at 20 dollars.