As you can see, the top app stands to make a healthy amount of money every day it's in the #1 spot, grossing over $250,000 dollars. Not bad for one day. The reality, though, is that the fall-off from the top spot is quite fast. The author of the blog post assumed that the #100 app would earn about $3000 per day, which is still not too bad.
The reality is that the vast majority of apps earn very little. Success in the App Store is based on luck, skill at game design, and having a good hook -- fame for another reason, something about the game that connects to something hugely popular, an unusual game mechanic, setting, technology, or twist that gets the app noticed and word of it spread virally. There's no standard recipe for being a success, more's the pity.
I continue to believe that making a successful app is an exercise in patience as much as anything else. Line up all the positive factors you can for the app, but be ready to try and try again. Perhaps repeated updates and new content and user feedback can turn a so-so app into a successful one. Or just improve your odds by creating multiple apps. But in any case, try to have as many advantages as you can for your app. If the app is similar to half a dozen other apps, you're going to have a tough time getting any downloads unless you have some other reason for people to try your app (You're famous? Justin Beiber likes your app? You're ready to spend millions on user acquisition? An award-winning artist designed the graphics? You have to have some reason that people will want this app),