They sell these pieces of shit like hotcakes, at the price they want to,
This is exactly the problem, demand far outstrips supply so they can get away with anything they want to and still have full order books. It has been this way since ASICs first came out and all the manufacturers have been the same. Until there is more competition in the ASIC miner market things are very unlikely to change.
You hit it to the point mate, they have total monopoly that's why we can't do anything and they can do shit without telling their buyers as what the OP has experienced. I hope that GMO who I think who is currently on production of mining hardware can compete with Bitmain's ASIC, it will be a great for us. At least we have options as compare to today. And in addition, lot of scammers claiming they have cheap mining hardware and many are falling for it because Bitmain can't deliver what they have promised.