Maintaining the program was potentially very expensive. Tesla promised that you'd get at least 50 percent of the base price as well as 43 percent of the options pricing. That wasn't a huge hit to the bottom line when the company was selling a relatively small number of luxury cars (Elon Musk even backed it with his own money), but it could cut much deeper when Tesla starts selling hundreds of thousands of Model 3s.

Look at it this way, though: while the move is unfortunate if you liked the idea of your car maintaining a high minimum worth, it's also a sign that the EV market is growing up. Tesla has enough demand that it can ditch the guarantee without worrying that sales will drop off a cliff. And with these kinds of volumes, resale value might not be an issue in the first place. There's clearly an audience for these vehicles, so you shouldn't have to lower your asking price just to attract a buyer.