This is much ado about nothing. The stock will go down tomorrow. All this is a a 5 1/2 year loan at 2.95% with an option to terminate and sell back to Tesla at a rate that is sure to be below market.
Now for the plus side... from a marketing point of view this will highlight the true affordability of a Tesla and will hopefully spur some additional reservations, however I do not see them going through the roof!
POI, in the conference call, Elon clarified that the residual promise is the minimum value Tesla will pay after 3 years. If the actual market value of the car is higher, Tesla will pay the market price.