Is that a serious question? If it was, then Labor costs is the short answer. The longer answer would also include unmatched economies of scale at every step in the supply chain leading up to the final manufactured product as well. So their cheap labor also gets them cheap components.

Disc-rot. -It happens but it’s not as common as its made out to be. In my collection it’s only occured in 2 out of 500+ discs.

apparently xbox 360 discs were particularly susceptible.