Well. I think the author got it wrong. He made me suspicious, so I checked the article he pointed to

A mission. I wanted to work on something I loved so much that I would do it even if I wasn’t getting paid. I had already spent countless hours in my spare time doing front-end development with Ruby on Rails for free, so opportunities to do that with people I liked and a product I loved would fit this requirement.

What the Author means, is that if you can do X for $200/hour, but you prefer doing Y for $40/hour, then do Y.