While Halo 3 is releasing right at the end of Microsoft's first fiscal 2008 quarter (which runs from July through September), Goldman-Sach's industry watchers are expecting the game to contribute about $170 million in revenue for the quarter, with more than 4.2 million copies shipped into the retail channel. That's nearly one copy for every three Xbox 360s in the world, going by the analysts' projections of an installed user base of 13.2 million by September.

They also note that the $170 million figure could be low by as much as $50 million if they've lowballed the installed user base. Microsoft's tendency to put revenue from games on its books as soon as they're shipped out could also boost the revenue number, as could any change to the analysts' royalty model, which assumes Microsoft keeps 80 percent of the retail price on first-party games.