I was surprised, at first, when I saw the "cost to purchase" figure of $6,811 for the car, because that's about what I paid for the car I commute in. Ah, of course! This is expected annual cost. Your use of an average price for a new car has a reasonable basis, but you assume that everyone will buy a new car for commuting, and that they will replace it in 50 months. My wife and I do, in fact, buy new cars, but only every 6 or 7 years, and she drives the car purchased new. I drive 36 miles to work, and my last two purchases have been 4-year-old models. I've had the current car 1.5 years and expect to keep it for 5 or 6 more; I had the prior one for 7. I think it would be foolish to spend the money for a new car when I'm going to put 20,000 miles on it each year, parking it in the sun all day every day, and this is not an uncommon opinion.
There are new cars in the parking lot where I work, but there are as many that were purchased used. These sorts of exercises are valuable, but they must be realistic if they're going to convert anyone. In order to present a true picture, you would need to include the average price of all cars purchased, not just new ones.