I see what you're saying and agree it is a factor, but I think you are omitting a couple of things. First, a BEV has significantly lower operating costs than a competing ICE, and that translates in to less depreciation. Second, the battery prices have already come way down. As the Model S came out, Musk announced the price would be $12k for an 85kWh battery in 8 years, which they are still sticking to (although the option to pre-buy it never materialized). If you stop by a store and ask a product specialist, they are currently saying that a replacement 85kWh battery costs $25k if you were to have to buy one now. Odd that there was no announcement for this; but perhaps that's because Tesla really doesn't feel batteries are generally going to be replaced, especially now that they are all under warranty for at least a few more years. They were designed to last 16 years - by then they may be down to 60% capacity, but that's still far more range than most BEVs currently on the road.