Hmm, This does not seem accurate to me.
Here is the info from the Tesla Web site:
Fueling with electricity instead of petroleum is a sound financial decision. Depending on utility rates, the Tesla Roadster costs as little as $5 to charge, equivalent to $0.02 per mile. Alternatively, a gasoline-powered car rated to 20 mpg costs about $0.15 per mile.
So it really comes down to what your electricity costs.