I leased a Mercedes C250 and the residual value of my car at the end of the 42 months was $25k or about $6k-$9k more than the book value of the car, depending on which guide you go by. I definitely was not going to buy it at the residual price, but was lucky to have benefited from lower payments on my lease due to the optimistic residual.
I turned the C250 back in to the dealership. After they processed and inspected it, noting it only had normal wear and tear, they offered to sell my car back to me for $17k($8k less than the residual) and waived the mileage fee I would have had to pay since it was 4k miles over. I gladly bought it back to hold me over until the Model III comes out, not realizing quite how long that would be!
Sometimes It Makes Sense to Turn it In
If your residual is much higher than the actual value of the vehicle, my suggestion is to turn it back in and see if Tesla will sell it back to you at a price lower than the residual. Obviously if you buy it, they do not have to go through the process of refurbishing the vehicle, the carrying costs, transportation costs, or paying someone to sell it again. All things that would encourage them to sell it to the original owner at a fair price. Not sure if this is something Tesla does, but I would assume.
Sometimes you are better off to buy it at the Residual Price and Sell
In the past I have leased a BMW and a Jaguar. The residual price of those vehicles was actually lower than the market price at the end of the lease, so I bought those vehicles for the residual and sold those for a small profit. I leased the Jaguar new with an $8k discount, so when I bought that for the residual and sold it, I ended up driving that car for $200 a month for 2 years after you take out the profit I made selling it. I did not do quite so well on the BMW, I only came out a few hundred dollars ahead, but did not have to pay the mileage fee to the dealership when I sold it myself.
When leasing you have to be creative when it comes time to turn in the vehicle.
You cannot always use the same strategy every time. If they hit you with a low residual, the good part is you even though you had higher payments, you can sell the car and make some of that money back.
If on the other hand you get a car with a residual that is way too high, like I did on my Mercedes and I would assume most Teslas, feel good that you are sticking it to the man when you turn the car in.
It does not hurt that they might just offer you a fair deal to buy your car back if you ask...