I think much better to buy antminer if antminer in bitcoin is sold out i think amazon is the only safe to buy it than buying antminer in alibaba because i heard a lots scammers out there..If you have paypal use it as your payment option so that you can request of refund if you didn't receive any product from amazon.
I don't trust to buy in alibaba since i heard a lot from some forum who bought some product and didn't receive anything.. And don't expect that you can buy lower price to any 3rd party distributor since antminer right now is in demand Mostly the price is $4k+ so if you really need the hardware to mine bitcoin well you don't have choice..
Amazon has no inventory but Amazon seller's quote them in average at $6.5K, still better option a cloud mining contract.
From your opinion on Alibaba it seems you have never bought anything from it, so stop the speculation and help the guy with the query instead of spamming to get some +1 in your counter. Ali does have a trader assurance for people to start business with providers but they charge 5%, pretty much you pay to Ali, and once you get the asset they release the money to the seller, so you have to trust Ali and not the seller as Ali is in between the business, it is good to start relationships with the sellers, but once you feel confident with your supplier, after several deals you can negotiate another payment and save that 5%. For this asset in particular, the S9; it is very overpriced, right now you can get a much more Hash rate from cloud mining options for the same investment. Also, depending on your order size it will be much cheaper to fly to China and do the research yourself and get real deals.
My $0.02