"Among consumers that would consider an electric car, the median extra amount that they would pay was $2,068. But 20 percent would pay nothing additional, while an equal share would pay at least $5,000 extra. Across major demographic segments, only one difference was statistically significant: 46 percent of consumers earning $50,000 or more annually would pay at least $2,000 extra versus just 27 percent of those earning less."
However, the current premium is estimated to be something like $10,000 for enough battery to move you 100 miles. Which means that unless gasoline becomes very expensive, it is going to be a long time before electric cars have any significant volume.