We're already to the point where if your commute is less than 8 miles or so, using Uber daily is cheaper than the cost of ownership on a $30k vehicle. Just imagine what self-driving cars will do to that equation.
The true line right now (where car ownership becomes more expensive than Uber) based on my experience is probably closer to an 8-mile commute and a $15k car. That line gets much lower when you add in things like financing, overpriced insurance, and leasing, which do affect a majority of the population.
I should actually do a writeup about this. I have access to all my numbers on it but I've only ever done rough estimates (which were clear enough that choosing Uber/Lyft was obvious). Now I'm curious to see exactly how the costs compared.
Which brings up the question: why the hell would anyone buy a $30k vehicle for 16 miles of commuting?! You can get a perfectly reliable car that's even reasonably safe and comfortable for regional road trips @ well under $10k, without even looking for sales or deals.
Until true driverless (no driver in vehicle, no insurance policy needed) happens, ownership will always be cheaper than daily taxi rides.
I did it because I wanted an electric car, and specifically a 2014 or later and there were very few 2014s for sale and those that were for sale were overpriced, IMO (in some cases, more than the net price of a new one).
Our other car is indeed a sub-$10K 2005 CR-V with 180+K miles on it.