However I think your assessment of car running costs is way too low.
The cost savings (or otherwise
) of an electric bike vis a vis a car are only appropriate if you have an electric bike
instead of a car.
If you buy a eBike extra to a car, your savings on the ebike are only on fuel for the car which even now is a minor part of the running and ownership costs.
In general you won't save anything on servicing costs because modern cars require servicing every year or 12,000 miles or similar so cutting the annual mileage on the car makes no saving there in most people's cases. Small savings on tyres, brakes, maybe but insurance, VED et all remain the same.
What I'm saying is, the economics of an eBike are even worse than they are generally painted. If I buy a new battery at £400 later this year, I will have covered 3000 miles on my Kalkhoff. That's 13p per mile. My small diesel saloon averages 55mpg overall and with diesel at 140p per litre, that costs 11p per mile...2p less. I know that this is a simplification, of course but it is a valid point.
I wouldn't attempt to argue the economic validity in the end, though. As Oscar Wilde said, that is for people who know the price of everything and the value of nothing.
My Kalkhoff enables me to travel with more ease, pleasure and freedom than any other form of transport I can think of. So long as I can afford it, I'll do it