Not sure how a used car with 19k miles can be worth the same as a new car. A Model S comes pretty well equipped unlike Porsche. You can get an AP2 75D with glass roof and power lift-gate for the mid 70s after tax credit even if you are not in CA, and it comes with the updated engine for significantly better performance. A used car at this level should be at least 10k below new to begin with. Given the higher than usual mileage and engine update and AP1 vs 2, that's at LEAST another 5k. We are at 60k max really.
With private resale, you are basically trying your luck to find a buyer who values your options. Under most circumstances, except for some essential Porsche options and AP on Tesla, most options are worthless at resale.