Deal is when an electric car with 150-200 miles of range is cheaper than a gasoline powered car, then for the vast majority of people the next car purchase will be electric or a plug in hybrid (twice the mileage of conventional). Assume 12,000 miles a year for a mix of cars
% Type mpg gal/yr ext
50% Electric -- 0 0
25% Plug in Hybrid 80 150 X 0.25 = 37.5
25% Non-Hybrid 30 400 X 0.25 = 100
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Total 137.5
100% Non-Hybrid 30 400 X 1.00 = 400
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100% 400
So the mix of electric, plug in hybrid and gasoline results in a 2/3 reduction in gasoline consumption.
And that's in the US. In countries without domestic oil production the choice will be made for you.
Some people will still pay for range or range at speed or less charging time.
http://jalopnik.com/they-drove-a-tesla-from-la-to-new-york-i... is a decent look at the state of technology. Driving across the US takes at least 12.5 hours of charging time, and averaged 65.4mph while ICE record averaged 98mph.
Even when "electric cars are cheaper on a capital basis", the technology will still be well behind ICE in some ways (and well ahead in others).