How much is next to nothing?
I'm talking manufacturing costs, I'd imagine it'd be <$15 to manufacture since it's basically 2 cameras and a microphone in a plastic shell.
The "good stuff" is all done in software.
maybe its the tv side of things thats costing more
I think it's simply because they want to sell it for that price, rather than anything specifically pushing the cost up.
Additionally, they have to be careful with what features they add/include because they will need people to effectively pay for them, but if they're seen as token features then people won't be able to justify to themselves the cost or value of those features.
So for example, they can't really insist that it's "worth" $100 (the difference in price, though the 360's kinect released at $150) because not everyone actually wants it. If it's a separate add on, it's very different because only the people who want one will buy it and see the value in it.
It's like the PS4 coming as standard with 4 controllers and them pricing it as such. It's all well and good for those who want/need 4 controllers, but for people who just want 1-2 controllers, they're just going to see the big price and not like it.