60 or 85?
There appears to be a floor on Model S pricing, because EV conversion companies and those using the batteries for other uses buy up high mileage used cars and/or wrecked and salvage vehicles for disassembly.
KBB says a 2012 Model S 60 with 150k has a private party value of 11,923 to 16,294, which I have never seen one go for remotely that cheap. Last I checked with people I know parting out these cars, the 60 pack itself was worth 10-12k, and the motor worth another 3-4k.
KBB says a 2012 Model S 85 with 150k has a private party value of 13,499 - 17,644, also far below what you will see the 85 battery pack and motor sell for alone.
Best estimate, I would say a 2012/13 Model S 60 with 150k of miles is worth low 20s, and a Model S 85 with 150k of miles is worth high 20s. And at those prices I would expect a pretty quick sale.