This sort of practice is not as uncommon as one might assume. It is extremely common for manufacturers to set a minimum advertised price (MAP) on the products

This sort of practice is not as uncommon as one might assume. It is extremely common for manufacturers to set a minimum advertised price (MAP) on the products they sell to retailers. This is done to keep the cost of, say, luxury goods above a certain value, or to ensure that even if demand falls off for a product, the product is sold from official channels at a price point that covers the raw-materials-plus-labor cost so the manufacturer isn't fundamentally selling at a loss. These agreements are generally enforced by both contract and tit-for-tat... Sometimes there are contractually-encoded penalties for going under-MAP, but sometimes the agreement is more "off the books..." If Amazon decides those Gucci purses are just taking up warehouse space and slashes their price to clear them, they can do that... If they don't want to have any Gucci purses to sell next year through official channels. Why is this behavior legal for manufacturers but maybe not for Amazon? I can see no other reason than the law is path-dependent and arbitrary. "Fair trade" is a concept we invent as we go. (Incidentally... As a consumer, it's useful to remember MAP exists when you hear whispers of "don't buy from unauthorized resellers." Sometimes the goods you get from those channels are shady, but sometimes they're exactly the same as the official-goods channels, shoveled into the back channel by an official retailer to clear warehouse space and reported to the manufacturer as 'damaged, lost' to preserve the MAP kayfabe).