Search makes ~$40B per year. They likely have over >3B MAU.

People that would realistically pay for the product - maybe 50M. I think a ~$10/m subscription could make sense.

The problem is - they probably need to offer something beside just being ad free. And I'm not sure what they could possibly add that wouldn't be better suited just improving the product for the other 99% of searchers.

I'd pay more than $10/m for Search if I had to. I pay for YouTube premium to get rid of the ads (and free YouTube Music). But I don't think the search ads are intrusive enough that I'm willing to pay $10 to get rid of them.