The margins on the servers Amazon buys are not that high. They are buying commodity servers, not the highly redundant high end ones. With just a couple of SATA drives. No redundant power supplies, raid controllers, hotplug ram and cpu and all the other high margin stuff that makes the server business really profitable.

Apple is probably more profitable for them. There was an old story that Apple designed their computers using a Cray supercomputer, while Seymour Cray designed his supercomputers on a Mac.