It looks like Sony got a better deal on many of the hardware parts. That's impressive. Being that Sony also makes phones, laptops, tablets, cameras, and smart TVs it leads me to think they may have leveraged the additional bulk buying of parts for those other devices for better deals on PS4 parts. Like they went to a supplier and said, "give us a better deal on parts for the PS4 and we'll also buy these other different parts we need for our phones/cameras/laptops/tablets from you as well." We all know you get a better deal by buying in bulk, but Sony could very well be negotiating to buy in even bigger bulk by combining supply contracts across numerous devices.
And if that is true then that only further speaks to the power Sony has in delivering great hardware at lower prices to gamers. If Sony can buy parts cheaper than almost anyone else can, then it's going to be very hard to compete with them on a hardware-to-price basis.
That's the best way I can make sense of these findings. I can't prove any of it though. I'm probably wrong. Interested to see if someone with more expertise could chime in on how Sony got such better deals than MS.