Don't underestimate the degree to which the market does NOT cater to niches. If 95% accept such vehicles with open arms for their convenience, the other 5% will be dragged along kicking and screaming whether they like it or not.
There are several things to note about this alleged failure of markets to cater to niches. First, it doesn't happen in the real world. For example, in the auto world, there are plenty of niche automakers and not all of them make ludicrously expensive cars. And if there is a large unmet need, then there's a natural way via the usual manufacturing process to scale a niche automaker to mass production automakers. Most of the brand names in the industry that are more than a few decades old were originally businesses of this sort that underwent that very same transition.
Second, it's worth remembering here that there have long been substantial non-market obstacles to automakers. For example, in the US you have to destroy a few cars in order for them to be determined to be road-worthy.
Third, don't forget the used auto market. After all, we still see Model Ts on the road in the US. Old cars don't magically disappear. And the huge number of self-driving cars will lead to a vast used car market for these vehicles. It wouldn't be that hard to refurbish such a car, especially one which already has the capability in some form, to be human-drivable.
Fourth, don't forget the car manufacturers. By your numbers alone, we have the regular car market dropping to 2% of the current market, while the bitter clingers will be 5% of the current market. Guess which market is still two and a half times as large as the other by vehicle count? And as far as profits go, that larger, human-driver market will tend to be more profitable per vehicle since it has "options" (high profit add-ons like seat warming or fancy paint coatings). A lot of these businesses might go out of business due to the large reduction in market size (of roughly a factor of 15 by your numbers), but not everyone will. And the human-driver market is still bigger than the other both by number of vehicles and profit per vehicle.