In the Costco model, Costco pays up front for the vodka and incurs all the risk if the vodka doesn't sell. In the Amazon model, Amazon charges third-party sellers "rent" to be on the platform in the form of a cut of all transactions, but the third-party sellers still incur all risk for inventory that doesn't sell. And then Amazon turns around and uses the sales data from the third-party sellers to undercut them later on.
I am not sure about Costco, but Best Buy does not purchase all the items it sells. For some items it only remits a payment to the manufacturer after the item has sold. Should they not get to see the sales data?
