True, but if owners are looking to return their Teslas en masse after 36 months the residual value will be a little less than the 43% they're apparently guaranteeing here.
It's not just a hedge against you ending up with a dud car either: you're also protected from a perfectly adequate '13 model's value being driven down by a new generation of Teslas which are drastically better (or better value). That's a worthwhile guarantee for the early-adopter of a physical product in a rapidly evolving market
Expect the most dramatic innovations from Tesla to come in 2017 and beyond then... :-)
Or that Tesla can sell "certified pre-owned" models for > the cost of the buyback.