> Secondly, that isn’t what sellers want. Many sellers use Amazon to fulfill their orders. Amazon is far more than just a “market stall”.

This.

Amazon is basically a huge logistics network. Their business is not selling you products, whether from their own generic brands, from high-end Veblen goods companies like Apple or from cheap chinese dropship artists. Their business is to process payment, and get that package delivered to your front door. To Amazon, their products is just a way to generate output through their logistics network.