From my understanding, apple is a "design" company. They don't have hardware manufacturing facilities. They design the PCB boards on PSpice equivalent programs and then contract out to various companies to implement these designs. Forexample, DVDR's, LCD's, HD's, batteries, trackpads, etc are all made by external companies.
The reason why apple has such good hardware is that they take the time to test it all together for quite a while before releasing it to the public. That is also why they have the slowest product development cycle ever.
BEN