Now, before you rush to call your broker with the intent to sell all your MSFT stock (or, more likely, proclaim in the comments thread of this article that this is a sign that the Xbox 360 is going under), hold on a second and take a breath. Cutting prices after a game has been around for a while is not a new thing. Some of these games have been available for up to 6 months: as Michael Pachter puts it "games are always discounted as they age, and last week's reduction of prices on select Xbox 360 games is part of this normal aging process." Going forward, he expects Xbox 360 games to settle into a system where we see the "first price cuts to $49.99 two or three months after release, and with $10 incremental cuts every 60 days thereafter." Just don't forget your change.
[Update: don't call your broker or your accountant. Well, you can if you haven't said hi in a while! Thanks youzer.]