Current price of battery is USD 200 per KWH. Over the time prices have dropped 80%. If the price drops to USD 100 per KWH electric cars will be cheaper than gasoline cars. Next would be to make the charging faster. New technology has shown it can charge 240 miles / 400 km in 5 minutes. Tesla currently does a full charge in 75 minutes. If charged faster, maybe you are OK with less battery capacity in your car.