So I have only around 150 sales of my book (see notes at https://andrewpwheeler.com/2024/07/02/some-notes-on-self-pub...). I make around ~$30 though net (average between on-demand print and epub). So my measly sales are about the same as the advance here (not clear if this was ever paid out, presume they would get it back if it was paid out).
If you really think you can sell thousands of copies the economics of it really should hit you.
I get going through a publisher will increase sales, but if you have a popular platform already to advertise it (like a blog or other popular social media), I just don't get it.