well you have to take in consideration profit margin.... for all we know MS might have a bigger margin than Sony.... which would make any guestimate on cost of production and material cost irrelevant.... for all we know the box could be 300 right now and the PS 350 with 0 profit margin.... or the opposite the PS could be 600 and the box 550....
anyway while I see the commercial advantage in terms of sales a Kinect less SKU could be at a lower price point I think it would be a terrible decision in terms of product.... the novelty of Kinect is fading.... if they don't put it in the box it will sell less than the old one even if it's better.... and it will be irrelevant... and there will be less chance for devs to have interest in it... anyone saying it won't change if it's packed... might be right.... but if it's not it will definitely have no relevance....
and at that point even if I will probably get an XB1 if it's not packed in all SKU at launch I will not buy this year one for sure and I will really look into the steambox as fair contender for my purchase...
