At current gas prices, and given the typical 5 to 7 year lifespan of a daily driver.
Industry average annual driving is 15,000 miles per year. The Volt costs $40K. It's twin, the Chevy Cruze, can serve as a decent comparison. It costs roughly half that amount. Let's be generous and set the gas price at an even $4 per gallon (a little higher than the current national average), and and the price of the Cruze at $20,000, and the lifespan of both vehicles at seven years.
Each car will drive 105,000 miles. The standard Cruze makes 36 mpg (and we'll stick with the optimistic gas mileage posted on the window sticker for purposes of the comparison. You will spend a total of $11.666.66 in gas over the 105,000 miles.
The Volt makes an EPA estimated 93 mpg. It will burn $4,516.12 cents in gase over the lifespan of seven years, a "savings" of about $8,000. You will not make back the $20,000 more that you spent on the Volt in the typical usage of the car.
I'm not sure where you came up with your various assumptions trapdoor, but I'll suggest - without choosing them out one by one, that each of them fudges the actual facts at least a tad, in favor of the case you're trying to make. Just a coupla for instances, the avg. yearly mileage is 13.5K not 15K and the average paid for a Volt is around $35K, not $40K and so on.
BUT...the fact that you (or your source) has stretched every average indice in order to make your outcome more dramatic, isn't dispositive in any case. For the Volt, or the Leaf, or even the Prius aren't marketed to the "average driver" and they don't need to be, in order to be highly succesful and relevant.
Let's consider just one indice - "miles driven". The fact is that many millions of Americans' average trip is 40 miles or less. Those drivers would buy virtually no gasoline. So...if we took the actual cost of that Volt, times the actual cost of the little gas they would buy, times the fact that buyers of this sort of car keep them longer than 7 years....all of a sudden, your anti-Volt case doesn't look so good, at least for THOSE drivers.
And sure, the Volt isn't cost-appropriate to ALL of a year's 12 million potential new car buyers. But it IS cost-appropriate to a quarter of a million, or half a million, or maybe a million or two. And whatever....that's one helluva significant market.