Cadillac has a luxury version of the Volt that sells for approximately the same price as the Tesla. No one buys it.
The fact is, comparing Tesla sales to Volt sales is idiotic. They aren't remotely similar cars and they aren't remotely competitive.
The Tesla Model S is outselling every single brand in its class. Porsche Panamera sales in California have fallen to non-existent.
I'd bet damn near no one shopping for a car in that price range who drives a Tesla would buy anything else. It's that good.