It's not, it's about half as I did this exact calculation a couple of days ago in a new car discussion with my partner (charging works out to ~£0.49 per 4 miles

It's not, it's about half as I did this exact calculation a couple of days ago in a new car discussion with my partner (charging works out to ~£0.49 per 4 miles, we're currently ~£1.05 per 4 miles for a reasonable mpg car driven primarily urban crawl) though note that thats retail charging, home charging is half that (about £0.25p per 4 miles)