I'm also assuming that if you are building a device that has a multi-year lifespan you can factor in the ever decreasing cost of components. Maybe the price of the components on day-1 are $500, but day-730 $350.
How this works with devices such as Kinect though I'm not sure. It's about attachment rates (extra controllers, batteries, etc.) on the hardware side
Then the software side has fairly obvious goals.