It's not just about the cost of gas.
There's more to this. The car that you buy for $70,000 (or $50,000 for the 160 mile version) isn't just a way to save money on gas. It's also an elegant, comfortable, high end luxury sedan. You could easy spend that on a comparably equipped 5-series BMW or Mercedes.
Tesla's strategy is the inverse of Nissan's. Instead of starting at the bottom and working up, they are starting at the top and working down. THis is particularly wise for several reasons. Profit margins are greater at the high end of the market, and volumes are lower, giving them a chance to get all of the kinks out of the design and the manufacturing processes before they introduce lower cost, broader appeal vehicles.
