They put a $499 hold on just the console alone so you can't go by that at all.
I'm guessing it may have some validity. Sounds about right anyway. Old Kinect was $110 MSRP at EOL I think.
$499 for just the console makes sense because well, that's the MSRP. They probably dont care w/without Kinect it's viewed as $499 of value since Kinect is useless without the main console but not vice versa.
Nintendo charges $140 for a replacement Wuu Pad (at least last I heard), and that too sounds about right to me. That leaves $160 for the Wii U console, and you can buy the 4GB Xbox for 179-199, and I'm guessing the BOM's are somewhat similar, similar die sizes, both flash storage based, etc. Also $340 base console makes sense compared to $399 PS4, ~same size SOC/hdd/blu ray, DDR vs GDDR. Of course it will not be perfect and I am not saying it is.