The most you can charge for an app on the iOS App Store is $999.99. In the early days of the App Store, a number of novelty apps came out, trying to make a quick buck by convincing gullible plutocrats to part with their money in the form of a $1,000 app download. The most notable example is I Am Rich, an iPhone app that literally did nothing except proclaim your affluence.
These days, though, the $999.99 club is made up of legitimate apps. Well, mostly.