It’s also not hard to argue that people accepted it because they assumed the additional money went to the government.
This is the same if you walk the chain backwards. Suppliers to Costco that simply raised prices and internally absorbed the tariffs are the ones due a refund, not Costco. Suppliers that sent Costco and invoice with a tariff line item should be on the hook to refund Costco (which means they should be seeking a refund from the US)