Many of the mega sellers don't actually have the product in stock. They sell items from many different companies and the company that has the product will actually ship it. The seller is a middleman. They sell it, contact the company that has it and tells them to ship it to the buyer. And I've even seen it where the company doesn't have it but yet even another company does. This is the case where companies buy groups(lots) of products. Say if a business goes under or something they would buy the entire inventory and they might or might not actually have physical possession of it and just find some reseller to sell the stuff for them. Quite common actually.