This July Microsoft is releasing a new collection of "Gears of Wars 2" add-on content (details here).
The retail version will include the Flashback, Snowblind, and Combustible map packs, which cost $5, $10, and $10, respectively, to download on Xbox Live, along with the new "Dark Corners" add-on, which has a new campaign chapter and seven multi-player maps. Cost: $20. A great deal.
But for gamers who already own those map packs, Microsoft is offering "Dark Corners" by itself for digital download. The cost: $20.