Cost of UHD Blu Ray - Is MS subsidizing Xbone S, or is Sony just milking it?

[mutantsushi]

JRPGfan said:

The chip inside the normal PS4 is bigger than the one in the Xbox One.
So MS probably save abit of $ on the cpu+gpu, and choose to include a 4k blu-ray drive as insentive for people to get the weaker console (xbox one slim instead of a stronger PS4).

Sony is also producing around 3x the volume as MS, so should be getting better volume discounts, as well as other economies of scale.
(selling alot more in Japan and Asia means less shipping charges proportionately to MS)
But the consoles are generally cost equivalent, even with equivalent drive units (as with OG, pre S/Slim),
so the question of Blu Ray drive is the differential cost issue, i.e. what distinguishes it from previous prevailing business model.