Aside from the top end A8s with upgraded engines, they get 18MPG city and 28MPG highway. Simply saying that the A8 gets 15-18MPG is deceptive. So, if we are talking range, an A8 will get upwards of 560 miles on a tank.

If you're comparing on performance alone, you better get the upgraded Audi to match the Model S...

Ok. That's a very guzzly car then, though; even other Audis like the A5 seem to do a lot better than that, especially on the highway.

Tesla's competition, from the perspective of performance and price, is very guzzly cars.

But big $100,000 cars like this mid-range S-class Merc http://www.mbusa.com/mercedes/vehicles/model/class-S/model-S... seem to have 20+ gallon gas tanks (here's the S550's capacity http://autos.yahoo.com/mercedes-benz/s-class/2013/s550/speci... ) and the ability to manage about 25MPG on the highway. That would place them at 500+ miles from a single fill. (They'll do a lot worse with city driving though: the S550 should only give 350 miles. I think these MPG numbers are the EPA's.)