That's a bold assumption. I can imagine a world where 99.999% of the web will be filled with non-human curated AI generated text.
The rate at which AI can generate text will be so much greater than what humans can generate.
The rate at which AI can generate text will be so much greater than what humans can generate.
You're already assuming pagerank and upvote systems won't break down in the future.
Presumably at some point computers will become (already are for all I know?) the largest consumers of content on the internet as well as its producers.
Now go ahead and spend $50 dollars on AI generated text nobody is ever going to read, just like almost nobody is going to read this comment.