I've been reading some books on the topic this week, and apparently juicing the sales by pricing books from $.99 initially to $2.99 long term leads to a lot more sales volume, though the royalty is only $.30 or $1 respectively.

A lot of Kindle books are discovered by "Also Bought," and apparently books won't show up there unless they've been bought by customers (even "bought for free" during once a quarter free book promotions you can run through Kindle).

The combination of lots of sales leading to lots of reviews combined with publishing multiple books (many indie Kindle authors have 20+ books published) apparently can lead to it being much more lucrative than just the statistics shared.

Though my own experience self-publishing my first book (non-fiction) through Kindle last year at $9.99 with no marketing is much more similar to what Jelly shared. I made about $200 total over the year.