If I am selling my used CT years from now which could have a residual value of les than 50% of the purchase price, but the FSD which I paid only $7K is now worth $100K, then I should be able to recoup the value of the new FSD.
Add to that the ability to incorporate the CT's regenerative braking when the RV brakes, thus adding to the battery pack charge until it's full. on a longer trip.