The Xbox 360 and PS3 versions will sell for $59.99, while the Games for Windows version will go for $49.99.
In related news, an update for the PS3 version of Fallout 3 is coming. It fixes some issues, optimizes the game, and adds Trophy support for DLC. Bethesda says that Broken Steel will be available next Thursday, September 24th. That will be followed by the release of of both Operation: Anchorage and The Pitt on October 1st, and the Point Lookout and Mothership Zeta combo on October 8th.
If you haven't jumped into Fallout 3 yet, this is the perfect chance.