The Bethesda Blog has announced that the Xbox 360 version of Quake 4 is being re-released at a new $19.99 price point on June 19. Currently, the only ways to pick up a copy of Quake 4 are through Steam (on Windows PC) and at the bottom of your local game retailer's bargain bin.
Or maybe your cousin Carl? He told us he liked Quake once. Borrow his copy!