Origin is currently offering between 30% to 50% off on every Dead Space game in their store. The first Dead Space is available for $10 as a PC download, and Dead Space 2 can be grabbed for $10 either as a PC download, or physical copy on PlayStation 3 and Xbox 360.
Dead Space 3 is on sale as well for $41.99 either as a PC download, or as a physical copy on PC or consoles. All the downloadable content for the newest entry in the series is also on sale, but come on. Don't buy that. Actually play the game and enjoy the experience instead of buying what amounts to acceleration cheats.
The Dead Space franchise sale ends on March 7. Head on over to Origin to nab a really awesome series for cheap.