Yeah, why IS it cheaper to get external drives and strip them?
I was looking at the same thing earlier.
Because when you type the serial into warranty checker, you'll discover they don't provide any on the OEMs. The moment you opened that plastic box (which a lot of are now permanently welded, so you can't put it back together) you released them of the biggest overhead they have at the moment - constantly replacing their poorly designed HDDs that some enthusiast cooked to death in poorly ventilated self built PC either locked up in TV cabinet or positioned under the table with exhaust vents tightly pressed against sofa while still under warranty.