A quick bit of browsing the Amazon Basics line of products would certainly lead one to assume they had totally knocked off the 3rd party products they thought they could without getting major brand pushback.
For example, the Amazon Basics guitar pedals are created by Nux pedals (the PCBs even have Nux on them).
So from what I can tell a lot of these are not ripoffs, just rebranded products. Amazon doesn't need to waste resources on manufacturing products that are already being sold on their site, but they can make deals with people that are already manufacturing those products.