Foxconn certainly pushes the limits of mass production, but Apple's engineers make their designers visions come to life and figure out how to do manufacturing no one else has done before. Johnny's CNC play ground - http://www.filmmakermagazine.com/blog/uploaded_images/ive2-7...
That photo is from a documentary [1] in which Jony Ive said that a big part of his work was designing fixtures that hold the parts in the machines.
I always figured that Apple designed the process and others merely implement that, they don’t seem like the kind of company that works with many ready made parts.