$9/mo is not going to cut it. Google's domestic annual revenue per user in 2019 was $256. [0] That's $21.33 per month. Not all of Google's revenue is from Ads, of course, but the vast majority is. (Let's ignore for now the valid counterpoint that Ads are increasingly served on other Google properties than Search.)
But even charging users $21.33/mo for an ad-free search experience most likely wouldn't be enough. By providing such an option, you'd greatly reduce the value of the remaining Ads pool.
The optimistic perspective on this is that if you are one of the users with disposable income, you're essentially subsidizing a great search engine and a suite of other tools for the less well-off ones.