Also, if the taxi fleet knows where everyone is going, they can easily organize a car-pool. If you're frugal then you'll be okay with pooling, pay more if you want the exclusivity (or, if you have the frugal plan, you can pay 10 bucks more this morning if you want to be left alone...).
The Jaguar vs Tata would make a fun algorithm. Say you're the frugal one, you order a car, and a Jaguar is heading your way. Suddenly your neighbor (on the premium plan) orders a car, and someone else a few minutes away cancelled their Tata. Oops, sorry, he gets the Jaguar.
Edit: Changed "Mercedes" to "Jaguar"
Same thing with the car age. They aren't going to cycle new cars in every few years. At best, they are going to replace the interiors in that time frame.
It also doesn't account for the size of the car. People buy 4 seaters for the 10% (or whartever) of the time that they have passengers. Commuters will be perfectly fine with a 1 seater if they can order a bigger car when needed.
The auto rental industry does. The average holding time in the rental car industry is 13 months. Enterprise Holdings (Enterprise, Alamo, and National) owns over a million cars. Lots of companies talk about "transportation as a service". Those companies do it.
Among other things, they own enough parking spaces to park all those cars.
They're going to recycle the cars faster than today, because they'll be used for closer to 100% of the time, rather than 10% today.
I don't see any reason to think a similar price-sensitivity wouldn't apply to other forms of seat-rented transportation.
First of all, what is a lot? 1% of the US would be around 3 million people, which is a lot of people and yet 1% is not very significant. Of course we know some people don't own a car, you can make your numbers look bigger or smaller depending on if you count them. (there are books on how to lie with statistics if you want to continue this line)
There are people who are already close to giving up their car who will.
I believe that most people will not give up their own car. Rush hour is a thing for a reason: most cars are driving during those hours, so your costs for a self driving car ride rental needs to account for that. Once your costs are not much different the utility of your own car is a price worth paying. I know that I can go shopping over lunch and leave my new toys in the trunk. I keep a spare diaper in my car just in case my kid needs one. When I go on vacation I often start packing the car a few days before.
If you are frugal rides in a self driving car is probably more expensive than rides in your own car. Your payment has to cover oil changes (I change my own oil - I've concluded that it actually saves me time over driving to a mechanic). Your payment covers inspection/cleaning after every ride - nobody cleans their personal car that often. People who ride in a self driving car will demand newer cars even though a 12 year old car (if well maintained) works perfectly fine for the same task.