It's also fascinating that they are running Linux internally nowadays, for their server side stuff. What next, I find out that all of the Microsoft data centers run Debian :) Considering that they employ all of those Objective-C and Swift engineers, you would thing that they would want to leverage their workforce write Obj-C or Swift backend code as well. For most backend tasks either Swift or Obj-C is as good of a language as any other.

Any way, rackable OS X systems are a missed opportunity for Apple. They can sell them to a company like yours, movie production houses, and even design some libraries and make a play for the web app market with Swift. Not sure how successful the last one would be. As for the economies of scale, they don't even need to manufacture or design the system, take an off the shelf rack mount server from another manufacturer, fiddle around with the casing a bit to give it that Apple feel, and load OSX on it. Perhaps the margins in the server side hardware are way too slim.