I said if you've already put in the effort to write the book, in which case that effort is a sunk cost.
There is more to life than money. Writing such a book allows me to share my wealth of knowledge. So what if I don't make a million dollars out of it? That's not the purpose. I want others to benefit so they can grow their businesses. And in turn create new opportunities for others.
You can't lose net money if you originally planned to publish it for free, though.