I highly doubt the 1k/50k stat - I have personally written 6 apps with more than that - so i've written slightly more than 1/2 of 1% of all apps in the app store with more than 50k users? unlikely...
Note in particular the quote just following the paragraph you are referring to: "For the typical app, less than half the people who download it use it more than once, said Guy Rosen, the chief executive of Onavo."