But cars last a lot longer than 5 years. And most people buying a used car are going to care about running costs a lot more than people buying new cars, so I expect the used EV premium to be substantial.

Any TCO analysis for keeping a new car for 5 years is going to be dominated by the trade in value. That's going to be a lot higher for EV's than gasoline cars, so I assert that you're better off financially buying an EV even at a $10k premium.

Aren't the drive battery packs the single most expensive part of an EV? Anyone buying a used one with any kind of substantial mileage can expect a harsh loss of range.

Sure, if you buy a Nissan Leaf.

To expand on this a bit, Nissan Leafs (Leaves?) are the only electric cars produced in significant quantity that rely on passive cooling for their batteries. Heat is the main enemy of battery health. So you can easily find an old Leaf who's max range is literally half of what it was when brand new. It depends a lot on how hard it was used.

Other EVs on the road are much better at managing battery health, such that it will never make sense to replace their main battery outside catastrophic events. If your electric car is going to die, it will almost certainly be from a bad collision, like any car.

Anyhow, the Nissan Leaf compares poorly on a lot of fronts to any modern EV available in the U.S. Most people in the market for an affordable EV should probably look at the Chevy Bolt first (now that they fixed the battery flaw that caused them to burn down). But if you're really looking for a cheap used EV and in the market for a Leaf, get yourself a Bluetooth ODB2 dongle and an app called LeafSpy to check on the battery health before you buy it.