You assume battery technology will not improve. It has been improving for many years, and will continue to do so. Batteries will get smaller and much more efficient. As the technology improves, and the market widens, the price will go down, the same way, as another poster pointed out, that PCs have done over the last 25 years.
The capacitance battery is a promising technology. I could see dropping one of those in my electric car after the old lithium-ion battery died. However, the cost of these batteries is quite high. You could buy lots of high price gas for the cost of one of them ($25,000). And if you do the math, and treat them as 100,000 miles of gas (their estimated lifetime), that’s over $6.00/gallon gas (equivalent for a gas car getting 25 miles/gallon using $4.00/gallon gas). I didn’t add the cost/mile for using the electricity which I heard was about $.12/mile. The electicity cost may shoot up if everyone is using these rechargable cars.
Another side effect is the production of ozone by these electric motors. Imagine an entire city firing up those electic motors in the morning.
My answer to this transportation headache is more oil drilling followed by the production of biodiesel with algae technology (or some other biochemical process).