I self-publish and make 70% list from Amazon, 65% list from Barnes and Noble, and right in the same area from my other points of distribution for my e-books.
For my print on demand paperbacks, I make about 30% to 40% depending on where they sell.
Yes, a contract with a publishing house might provide a little stability, but in terms of making money as a new writer, the self-publishing world is a way to at least start bringing some money in.
It certainly appears to be so.
In the 1970s, I was working for a manufacturer of a couple of products that had craft potential. I developed 25 or so projects for the stuff and they wanted to publish these as a How To book.
IIRC, the advance was $1k and the royalties were 5%. I was also committed to giving presentations (the “pre-order” gig the author mentions).
There were many accounting tricks used by the publisher to reduce the royalties. It was not uncommon during the first year for the statements to show negative royalties, meaning they were subtracted from the advance. The company employed salesmen (back then, it was mostly men)and these guys were not at all happy to see a 20-something girl selling *their* territory. They received the commission on product orders and I only received the book royalties+expenses, but they behaved as though I was an imposter stealing their paycheck.
The life of this sort of book is brief. The author likely never recoups the advance. From the outside, it seems that a self-published fiction series would be a better chance for some income.