The thing about the cost of having a car is that there is high structural cost (i.e., the car's depreciating just for sitting around, the financing or opportunity cost of buying the car while waiting years for that value to be depreciated in use, and insurance) and low marginal cost for using it (i.e., fuel & maintenance), so when folks make the determination that a car is absolutely needed, they buy the car, but then make a cost-benefits analysis on using it based on that marginal cost of operation. This paradigm (I always like it when I get to use that buzzword, LOL) will be completely uprooted in the upcoming era of the driverless car, since the driverless taxi will eliminate that structural cost, making the cost-benefits analysis be the net cost of the vehicle instead of simply the marginal cost.
As for the cost-per-mile that the author quoted, Uncle Sam has the rate as $0.545/mile, but an older or cheaper car would have a lower net cost. As I myself have a VW (Jetta Wagon) with about 170K miles, bodywise in "rough" condition and with a Check Engine Light issue that the thermostat needs to be replaced - a $550 job that I calculate, based on the lower gas mileage and low usage would take me about 10 years to make it worthwhile, and thus I am not getting done since the issue causes the engine to run a little cool when operating at high speed on a cold day (the thermostat is stuck open, thus always cooling the engine whether it needs it or not, and not the much more important issue of it being stuck closed, which would result in an engine that would NOT get cooled), and I fully expect to be using driverless taxis by then - only has a wholesale value of about $300, LOL, so there is virtually no opportunity cost being lost. All that said, it does seem like every few K miles, there is another $200 job that needs to be done, and I have determined that my cost of operation is about half the federal rate; I am sure that someone with a Moustachian outlook could get his costs down to something nearer that than what what the author posits.
As for the author saying that walking or biking is a solution, it is only a solution when the distance is low, in which case that marginal cost will be proportionally lower as well.
I do agree with the author that IF someone were to determine that what he needs transportation for in life can be met by walking/biking or mass transit - and now the at least somewhat economically sensible option of human-driven Uber, to be replaced by the much more economically sensible option of the driverless Uber - then it does not make economic sense to own a car. Of course, the important BUT to that rationalization is that can only happen living in a very urban area where everything that person needs - shopping, entertainment, and most importantly a JOB - is near there (although Google et al with their employee buses makes the latter not an issue, but how many employers are like that?). Living in those kinds of places is very expensive (for the space), and as well, makes job opportunities outside the immediate area a hassle, involving a long, typically SLOW public transit commute or a residential move. Case in point: the author refers to Seattle, but Seattle is very expensive! Someone deciding to live in suburban Kansas City would save much more in housing costs to make up for the extra costs of owning his own car.
Oh, and while biking could be OK, even I, someone who likes to exercise, sometimes don't like to exercise at a certain time (which I would be forced to do if I had to bike), and what about when it is raining or snowing, etc. And also, let's not discount the fact that someone being seated in all that extra metal that being carted around would be much, MUCH safer in an accident than a cyclist. (NOTE: I think a well-engineered small car can be as safe, if not safer, than a clown car SUV.) And while cities like Seattle might be safe, some of us live in cities where the downtown areas are quite dangerous.
Holistically, it seems that the author is saying that folks should choose to live in smaller, cramped spaces, with roommates that are not family (or SO) so that the amount of money saved by living out in the 'burbs can be devoted to high cost of living downtown. Well, I like my safety, space & privacy (I early on, even as a bachelor, bought a house so that I could have the room for a nice gameroom, and piano, etc.), but I did buy in a lower-cost suburb that was not too far from work (the work was out in the sticks a bit, so public transit was not an option). And while I agree with the Earth-saving gestures, I think the author comes from the POV of the typical young, urban, coastal demographic that fails to see that folks living elsewhere have a different set of lifestyle wants and transportation needs.