That's exactly the type of questions KBB attempts to answer with their estimated resale value of cars built recently. Nobody said it was an easy task or that they will get it right within 0.1%. But there is also no reason to think it's an impossible task to come up with a reasonable and educated estimate of future value. They certainly have the access to the kind of data one would want and the experience to make use of it. And they might make a mistake or future market conditions could change in unexpected ways. I get that. But I see no evidence that their estimate was politically corrupted or they are trying to do Tesla a favor here or they are incompetent. The Model S had considerably lower depreciation than other cars in its price range and I find it reasonable that they would rate the less expensive Model 3 as having a little less depreciation relative to the Model S.
While I agree, it's not an easy task to estimate future values, especially of such a unique car, I don't think it makes sense to throw ones hands up in the air and say "We might as well just throw a dart at a dartboard". No, KBB takes their years of experience of used car markets and what they know about the Model 3 and, using all available data and reasonable assumptions, makes their best estimate. It's not the word of God but it's better than a wild ass guess and I'll take it over a non-professional Internet armchair guess any day of the week.
Even though I don't plan to sell either of our model 3's anytime soon, I find it heartening that auto industry experts are projecting very low depreciation rates relative to gasoline counterparts. There is no evidence that KBB is biased toward Tesla or EV's.
