Electric car company Tesla's success -- meaning the Tesla S sedan -- is being driven by the wealthy, especially those on the west coast. Jessica Caldwell, auto analyst at Edmunds.com says it's the most-registered new car in eight of the nation's top 25 wealthiest zip codes, measuring by average real-estate values. In Atherton, Calif., where the average home price is $6.7 million, Tesla has a 15% market share. Caldwell says the car could have huge success if it comes out with lower-price cars.