"The Xbox is a BIG console. You probably get like $20 more in the extra plastic and power brick alone. Sony gives you some generic power cord."
I think Xbox One is built more quality too,. At least the impression I got/get is PS4 has more reliability problems, is louder and less refined, looks and feels cheaper. The DS4 has quality problems, etc.
Now you could probably argue that it's smarter to skimp a little on quality to hit a 399 price and pack in more power too, as Ps4 did.
Microsoft was so spooked by RROD they overbuilt the One, and yes I think it probably adds like $20 to the cost vs PS4.