This.
To me, the real issue here isn't so much the cost of out-of-warranty repairs or the crazy high deductible structure for the extended warranty; it's those things *combined* with Tesla's reluctance to come up with a solution that allows third-party shops access to service information. Tesla's policy (for the moment) basically forces you to go through the SC for even out-of-warranty work, and anyone with any high-end car can tell you that not being able to use an independent shop is a recipe for extremely high costs.
In the long term, it's not sustainable. For many high-end customers, it's not going to be an issue, because they'll simply trade their new or CPO Tesla in on a different one before the warranty runs and the only thing they'll get hit for is the ridonkulous $600 annual service. But what are the next people in the ownership chain going to do? What about the people that bought the car on the theory that an electric drivetrain should mean excellent long-term reliability? Especially those folks that stretched to buy a very expensive car after factoring in what they thought were lower long-term costs of ownership?
More than anything else, this is what I view as the existential threat to Tesla's growth from a niche producer (where they can afford to take great care of every customer individually, like the limited pool of Roadster owners) into a mainstream automaker. We'll see how they handle it.