Its quite amazing how much money you can make with self-published books. For example I wrote a book about Decoding CAPTCHA's. I have the top ranking post on most search engines for this which is the only marketing channel. I collect about $35 a month from it without spending any additional time marketing. Not very much but such a small niche it really surprised me. Oddly enough the main reason for writing the book wa…
In what way does the first claim follow from the example?
It might be possible to make a lot of money from self-publishing books, but $35/month, whether with or without additional marketing, is hardly a proof for that.
If anything, it's a proof of loss, as the book took you time to write. If you value those hours at the minimal wage rate, it would take ages to recoup those costs...