Another point about Carvana, is I don’t see how their cost of acquiring cars will ever go down. They are buying used cars! From what I understand auctions are a big source of their inventory. Someone has to sit there and inspect the car and decide what to bid. And bid on it. And have it delivered. This will not scale either. In other words it will be very difficult to scale down OpEx for Carvana on the purchasing end.
Compare this to, say, Wal-Mart, who probably has ERP software sophisticated enough that it sends purchase orders to suppliers automatically with no human intervention, and inventory just shows up on their dock. Prices are negotiated/arranged beforehand for many purchase orders over, say, 6 months or a year.