All I know is I started with $10 worth of STEEM 3 years ago, and I've left a comment every day since then, which almost always pays out at least 5 cents. I also curate every day at least 6 or 7 posts/comments. And I am currently at a grand total value of $8.
My comments suck so bad that 3 years of them has LOST me 2 dollars.