We have a decade of data on the question of how much degredation there is for EVs. Short answer, not much.

https://storage.googleapis.com/geotab-sandbox/ev-battery-deg...

In the UK, the government also pays for the dementia and asthma that the car pollution creates, and importing the fuels is a cost, as is the lost efficiency, cost of meeting net zero targets and upgrading the grid (which EVs help with) so it evens out.

As I say, they'll probably start taxing them anyway, and thats good, London has a "Congestion Charge" so exceptions for EV make sense as a short term incentive, but they still cause "congestion" and should still pay.

In some degradation curves for lithium batteries, it looks like degradation is linear down to 80% over around 150 cycles. From then it degrades to 0% over another 100 cycles.

From the curves in your link, it seems EVs have fewer cycles per year than mobile phones or laptops.

But after 15-20 years, their batteries will still most likely be dead.

Average age of cars in the UK is 8.4 years, it's growing, but slowly, the 13 years+ segment is about 1/5 of the total, so as long as 1 out of every 5 batteries makes it that far, we'll be fine, anything better than that is a plus. Plus we can start making the new batteries from the 20 year old dead batteries rather than mining fresh materials for them, if we can't find any other use for them.

The average /lifespan/ of a car in the UK appears to be 13 years which I think means we currently expect half of cars to be used for longer than that. EV batteries apparently have 7-8 year warranties, I assume that's the result of a lot of careful consideration.

We can expect battery tech to improve in the next 8 years, and hopefully become cheaper, but a move to EVs could still drastically limit availability of cheap vehicles for those who need them.