There's a very limited number of supplies at participating Microsoft Stores. On May 7, we launched a pilot program at Microsoft Stores in the United States to test a new pricing model for the Xbox 360, said a Microsoft spokesperson in a Joystiq interview.
The price of the deal after adding up all the costs is about $460 ($99 up front, plus $14.99 monthly subscription for two years), which is significantly higher than the standard price of the Xbox 360 with Kinect at just $299.
The key difference between the standard price and the $99 deal is the cost of Xbox Live. If you're a user who plans to subscribe to Xbox Live, you could save significant cash by purchasing a bundle and then Xbox Live separately. Standard two-year subscriptions to Xbox Live cost $59.99. In the long run, if you're able to pay the money up front, you're better off getting the normal-priced Xbox.
If you decide to purchase one of the $99 deals, you also run the risk of quitting Xbox Live early. Microsoft charges a termination fee, which could be up to $250 depending on how much time is left on your contract.