I wonder how many people choosing to write books, are expecting it to be a profitable use of their time, and make more than pocket money?

The article mentions the publisher saying that their median book sells in the single digit thousands, so half of the books are selling less - perhaps hundreds rather than thousands. If you are making a 15% royalty on a $50 book selling a few hundred, or few thousand copies, for something that probably took a year or more to write, then this is obviously more about the satisfaction of doing it than being a worthwhile financial endeavor.

Are most people choosing to write books fully expecting that it may only make a few thousand dollars?