Most of the stuff from Amazon is actually resellers like the ones on Ebay and factories don't warranty products sold from those sites. If you search around you'll find the same stuff cheaper. I know this because I'm a professional buyer, you can save money on shipping using prime even if you have to pay more for the product in some cases.
I use Amazon Prime in a "professional" manner as well, being in small town Madison there is little here for shopping. I could drive about 25 miles to find some things but why do that when I can have it on my doorstep.