Personally, I've made a relatively trivial amount of money from the books I've written, but I have little doubt they've been good investments of my time--some of which has been work time.
ADDED: I'd add that "promoting your book effectively" probably isn't free. Most authors aren't going to get a lot of publisher support so now you're hiring a publicist, paying for review copies, paying to travel (normally) to speak at events where you do book signings and promote your book, etc.
"A 98% drop in sales after the first year, Seventy percent of traditionally published titles fail to pay out a single dollar in royalties, Vanishingly few nonfiction books sell even five hundred copies"
I.e. you can't just slap a book together and think you've got credibility. People see right through that.
This is something Tendayi Viki of Strategyzer talked to us about:
"HOW DO YOU THINK ABOUT THE BOOK AS A PRODUCT? In my line of work, credibility is very important. I can’t cold call companies and be like “Hey, you know that those innovation programs are very important? Well, we have the best one. You can buy it now for three easy payments of 599.” Reputation matters a lot. It’s so much easier if someone comes to you. If they already respect me before we start the conversation.
Now, there are two ways to do that. You can deliberately be the snake oil salesmen. But that’s why those books don’t work because it’s so obvious what the person is trying to do. They write a book so they can say “I wrote a book”.
Or, you can say “I actually have something authentic to share and let me share that.” That’s the approach I’ve taken. I know I need to build a reputation but I don’t want to build it on nothing. If people pull back the curtains, they can see substance."
Notes I want to make it clear that I'm not accusing you of saying that. I'm merely adding to your comment.
Reference https://writeusefulbooks.com/resources/Tendayi-Viki/
It also explicitly is calling out methods that do not require fame, nor does it espouse a goal of fortune (unless you treat a living wage as a fortune).