This confuses getting to the top (which depending on the algorithm could just need a small initial spark aroudn your app) with staying at the top. Apps that stay at the top for weeks on end make lots of money -- up to several millions per year. As for the App Store, just like ANY OTHER marketplace, it won't make you rich in itself, just for appearing there and "putting the work"...
Paid Mac apps, no. The article is about the Mac App Store, not iOS. Even among iOS, however, the most successful apps are free ones with a viral incentive to do in-app purchases.
Most of the top apps have an external influence. 4 of the top 10 come out of Apple. Look at top games on Mac - most of them are major publishers. Even "independent" apps had a following outside of the Mac App Store, like 1Password.