I bet they make money on some people, who just don't buy much from them. But even if they lose money on Prime, they'll make it up on their margins, as you sugge

I bet they make money on some people, who just don't buy much from them. But even if they lose money on Prime, they'll make it up on their margins, as you suggest. There's also a TOS, maybe they have some loopholes - http://www.amazon.com/gp/help/customer/display.html/ref=hp_primeland_resources_tc?nodeId=13819201 http://www.amazon.com/gp/help/customer/display.html/ref=hp_p... They don't guarantee squat, and not everything is eligible. Also, they can terminate the contract and give you a refund. I'm guessing that it's pretty rare though. Most people will either buy lots of stuff (Amazon's happy), or not buy lots of stuff (Amazon's happy).