How Do People Make Money With Kindle Unlimited?

I'm pretty new to erotica and took the plunge with a few shorts recently. I think I'm doing pretty well, and I've been getting some sales and lots of reads.

On my latest short, I received a bit over 6000 pages read. From what I can gather, that's about 20 dollars for people reading 200 copies of my story.

Coming from writing in another genre, having people read 200 stories is pretty exciting, but the money seems a bit sad. Are the successful people here having tens of thousands of copies read? I'm really confused since people say to sign up for Kindle Unlimited, but it seems hard to make much money through it.