If anything, I found his post discouraging. He's built a great app and only managed to get people to notice it when he made it free. If a top20 app only managed to earn under $500 what does it say about the current state of the app market?
I wish we could have seen revenue numbers if he had put ads on the app the day after he shot up the popularity charts and was doing 10s of thousands of downloads a day.
I'm thinking of that story a couple months back about the Bible app, how there were a few but they all sucked, and people had decided that downloading the bible onto their phones was something they wanted to do.