Costco is maybe not the best example, because nearly every Kirkland product is a main name brand with a different name. It's almost never the case that Kirkland

Costco is maybe not the best example, because nearly every Kirkland product is a main name brand with a different name. It's almost never the case that Kirkland coffee (often made by Starbucks) is on the shelf next to an identical/equivalent coffee from, say, Folgers. Costco often only stocks one type of each product: they have Kirkland batteries (Duracell) but no Energizer (though they do sell other Duracell batteries at a higher cost). Most supermarkets, on the other hand, work with manufacturers that aren't name brands, and almost exclusively sell their store brand alongside name brand products. While I don't know what makes Amazon's practices different from what supermarkets do, my assumption is that placing two products adjacent on a shelf is very different then highlighting and promoting the store brand above and ahead of the competition. The store brand doesn't appear exclusively in recommendations or ads or come with a "Preferred" badge. The store also doesn't use sales data to decide which products to make a store brand for, with the goal of overtaking the name brand.