IMO move will not get the burst of sale that Kinect will (if it becomes successful) however I doubt that it'll be a complete failure. Instead move will gradually find its way to become integral part of both core and casual PS3 base, it may take a while but inevitably people will pick it up.
It may not seem like a whole new innovational product at first, but the technical aspect of it opens up a whole new peripheral for the devs that Wii limited control couldn't do. It will take a while till so called those killer apps are released but when it does, people will embrace move.
So yeah don't expect it to be the best seller at xmas, but it won't flop that's for sure.
Edit: To answer your question, its easy if the profits cover the initial investment then it is technically a success. The important thing is the hardware sales, if hardware sells, software will follow.
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