Interesting. I looked on Auto Trader and according to them the cheapest Nissan Leaf, brand new, was £27,000. I then looked for 3 year old cars with average mileage. Prices seemed to start from £7,000. Hardly “free” motoring over 3 years!
Doesn't seem particularly different from what you'd expect of an equivalent gasoline-powered car? Not brilliant admittedly, but if you're doing 10,000 miles a year in a gasoline car that averages 40mpg you'd be spending something like £1500 a year on fuel which would offset the depreciation a bit.