What is the ruling on trading through the "Amazon FBA" method, where goods are purchased from the manufacturer and sent directly to Amazon warehouses, then advertised and sold through the Amazon page, with Amazon storing the goods, shipping them to the customer, and receiving returns, in exchange for a fixed warehouse rental fee, packaging and shipping costs, and a percentage of the selling price ranging between 7 and 20% depending on the type of commodity?

There is no objection to operating in the manner described, provided that the commodity is not sold to the customer until it has been purchased and moved from the factory to Amazon's warehouses. This is due to the Prophet's (peace be upon him) prohibition of selling a commodity before it is possessed and taken into custody. There is no difference between transferring the commodity to your own private warehouse or to a rented warehouse on Amazon. What Amazon takes for its services is a permissible fee, whether it is a fixed amount or a percentage. It is permissible to grant the buyer the option to return the commodity for a known period if he is not satisfied with it.