I think it's more that the $4B Hertz order is a big vote of confidence from a big rental car player that signals a higher likelihood of all the other big rental car companies (since this made the news, I'm assuming other big rental car companies haven't done so, or at least on that scale, at least for an "ordinary" vehicle, since a quick search shows you can rent a Model S from Enterprise, but only from their Exotic's section) to follow suite, and a potential ensuing continuous revenue flow for Tesla as these rental cars end their life-cycles and need to be replaced. Of course these are all just possibilities, essentially bets.