You can return most things you buy from the physical Apple Store under ANY term. Well, I haven't tried removing the internals and returning it. It's a "no questions asked" return policy. Usually it's for 14 calendar days.
http://store.apple.com/au/help/returns_refund
If it's bought online, it has to be returned through a courier which Apple arranges and pays for.
Wait....they do? I've returned many-a-macs and I think I've paid for shipping every time.