Prices would get even worse, that’s the point.
You also shouldn’t assume that if Nvidia exits the consumer market that AMD/Intel would even try to fill the gap. The corporate world is very much trend following, and if Nvidia left entirely AMD/Intel are more likely to decide to follow Nvidia’s lead and also exit.
It wasn’t just it has to run on both variants, they required full feature parity. And the series S was way weaker hardware than even budget PCs of the time.