I look at it this way. If uber was cheaper would I be calling an Uber every day or would I still want and use my own car.
I'm still going to want and use my own car. Cars will still be sold. I don't think robo taxi is going to be as big as everyone thinks. Is anyone here going to sell their tesla for an Uber with no driver? I like owning cars, trucks, motorcycle toys.
The hugeness depends on the cost of autonomy, which would depend not only on the ultimate system cost, but on competition. The more companies with systems, the more competitive pressure there would be to have direct sales to private buyers.
However, it also depends on what happens with advanced driver assistance, because people would be choosing between being driven, and driving themselves. The better the assitance, the smaller the advantage for autonomy.
I think the biggest thing to consider is the potential impact on the used market. The used market is twice the size of the new vehicle market, and it's populated by value seekers and the capital poor. Offer those people an option that still has the convenience of point-to-point travel, but at lower cost, without financial burdens, and with the benefit of not having to drive, and I think you'd see huge demand. If you hit used car demand, you lower resale values, and that has a knock-on effect on the new vehicle market.
Add to that the new-car buyers who're in that market partly due to aversion to risk.
Also add to that people who end up carless, for example coming off leases, or with a write-off. Those people would previously have needed to buy, but would now have the option of using an AV service, removing pressure. Removing pressure to buy is something likely to hurt car sales.
Add it all up, and I think you have the potential for a significantly reduced market, which would be painful for a car industry so dependent on scale.
Given the dependency on scale, that would also be a competitive pressure to sell AV systems directly to consumers in order to raise vehicle sales. So, you could end up with a large reduction in sales, followed by a bounce back.