Tesla value calculation at 40 P/E = $298 to $373 just based on 2014 production levels
Tesla estimates 40k cars next year (they will likely produce around 50k cars as they have a history to produce more than they project.) With the average price of $90k at 25% profit = $900MM total profit, at PE of 40 the stock is $298. If they do 50k cars, then the price is $373. Tesla has explosive growth so the PE is justified and may actually be too low.
Due to savings in gas, maintenance, and the fact that the motor can last over a million miles and the aluminum body never rusts, the effective cost of ownership is similar to an internal combustion engine car that you can buy for about $50k, and this is without even monetizing the safety, technology and performance features unique to Tesla.