If your car gets x mpg in the US, your cost of gasoline over the lifetime of the car is about $1M / x. ($5 per gallon * 200,000 miles / mpg) So a 20mpg SUV will cost you $50K in gas, or a 50mpg Prius will cost you $20K. (Pro-rate if you're just keeping the car a few years, of course.) If the price per mile for electric is equivalent to 100 mpg, then it's going to save you only $10K over a Prius, but $40K over an SUV.
I live in the San Francisco Bay Area. A lot of the driving I do is less than 10 miles each way, but there are a lot of 40-50 mile trips that I make frequently (one is to work, on the days I don't telecommute), also between Silicon Valley and SF or Berkeley. I'd need a car with at least 200-mile range that I can charge at home in 6 hours to feel really comfortable driving that. If I could afford to maintain three cars (I don't have parking for them, and would rather not pay for the insurance and registration), I'd be fine with the current electric cars, which would get used for most non-commute driving, but my wife and I would still have full-range cars if we needed them, though I'd rather wait a few years.