EA is currently running a 50% off promotion on the Xbox Live Marketplace, which includes all Dragon Age: Origins DLC aside from The Stone Prisoner. Awakening is 1200 points, Warden's Keep, Leliana's Song, and Witch Hunt are 280 points each, and Return to Ostagar, The Darkspawn Chronicles, and The Golems of Amgarrak are 200 points each. It's still quite a bit cheaper to pick up the Dragon Age: Origins Ultimate Edition bundle pack, but if you already own the base game, this is a good week to do some upgrading.