How successful is CarVana exactly?

Just saw one off I-10 here in Houston. Although a very cool concept, how do they turn a profit? Infrastructure alone has got to be 500k-1M and with only a handful of cars to choose from, not to mention they have to lease that space for X/month or year. You'd have to flip those cars on the reg to keep in the black.

CarVana main page

Anyone have any experience with that company?

ETA: didn't know they also sold used cars