A writer pointed out to me that writing a book is very similar to building a tech startup. The hours are long, it's critical to build a strong platform and there are the same swings from despair to elation.

Additional data points are always very much appreciated and it's very good of the author to release his tools and methods for others to learn from. Of course, the $5k in 2 weeks doesn't account for the time it took him to write the book or the opportunity cost of not taking other work, so this still might not have been a financially worthwhile venture, but hopefully it will keep selling and he'll publish more about it.