Maybe it's a production price and they'll sell it at a loss? I really doubt it'll be that damn much. How many people actually paid 100 bucks for the wireless or the steering wheel? I know I sure the hell didn't.
It'll need a killer app to move at that price.
Not just some novelty Wii Sports-esque thing or some retro-fit version of HALO.
It'll need its own game built from the ground up, that uses what Natal has to offer (that other motion controls can't) and captures the hearts and minds of the nation (and in turn the globe). And god help us if they think that "Milo" demo is it.
And I'm not saying MS isn't capable, it'll just be a wait and see prospect at this point.
Until they reveal such a thing, I'm not personally going to drop $100 or more on it. At least to date the PS3 Move has had a ton of really fascinating tech demos that have got me on board, and I've owned a PS3 eye camera for years, so my cost of entry on the Move is going to be much less than $100.
"And the book says: 'We may be through with the past, but the past ain't through with us.'"