But then I look at the article. Oh, it's over six years? Okay, $26k/yr is a lot less and all of a sudden it's a big risk to try and turn that into a real business. Wait, what's that in the screenshot? 78 books? $341 per book, per year. And my thought goes from "that sounds like a great little business!" to "fuck that" within about fifteen seconds.
And such is the lifecycle of these "how I made $n doing x" articles. Great claims that when you dig into them, the resulting wisdom is basically "do a lot of work, and have a little bit of luck. And don't forget the marketing!"
I don't mean to tear down what the author did by any stretch, it's impressive regardless of the time frame. But if you're already making $150-200k/yr from a tech job, do you really want to bust your ass for another couple grand?