Not a monopoly but Amazon Basics products are copies of Amazon's best selling products at a much cheaper price. This makes third-party vendor competition pretty harsh. I can buy a Rain Design mStand Laptop Stand for $40 or buy the Amazon clone for $20.
I have the Rain Design stand, and out of curiosity I checked those just now on Amazon. Seems Rain Design has suffixed their product with (Patented) now. I'm guessing they are less than thrilled with Amazon at this point.
The Amazon Basics items I've seen could be described as "the minimum acceptable". It's better than the typical Chinese junk, but anyone upmarket shouldn't have to worry.
Then it was a genius idea. There's tons of awful, broken stuff for really cheap on Amazon. With basics you get something you can at least know it works and if not can complain to someone.
