Costco is not only curating the selection: most products you buy there are created specifically for Costco, even if it's not the "Kirkland" brand, it's an SKU you cannot find elsewhere. Amazon would need to figure out the process of creating such products first and I see it's been trying: there are "amazon basics" brand products and even house brands ("Denali", I think, is Amazon's tool brand). The problem is that unlike Costco, Amazon cannot offer much to the suppliers of such products. Costco gives a limited shelf space in their high traffic stores in exchange for a discount and warranty. What can Amazon? Only thing I see is "amazon basics" being a bit more valuable than the brands like GOOLOO or MEPTY.