The total cost of the contract comes to about $360, but that's a wash if you're going to be getting a Gold subscription anyway. Microsoft's been pushing the low-cost 4GB Xbox model for a while now, and along with the Kinect, it makes for a formidable competitor for the Apple TV as a $100 media center. The $15 per month is more than the current cost of a Gold membership, but that could be offset by additional media streaming services offered in the plan, like the Spotify competitor Microsoft is reportedly showing at this year's E3.
You can get Xbox Live Gold for $5 per month. And the 4GB Xbox 360 with Kinect for $300.
That is not a wash, that is a rip off.
(24 * $15) + ($100) = $460
(24 * $5) + ($300) = $420
And if you buy Xbox Live Gold in 12 month groups you can get it for $4 per month:
(24 * $4) + ($300) = $396