This really kinda ruins the whole app store on many levels.
The App Store functions under an almost perfect free market model. downward pricing is actually a GOOD thing. It means that a true equilibrium is possible. The reason why their aren't $20 apps in the store is because no one has made an app that is worth $20, or if they have someone else has made one similar and cheaper.
The idea of an app store that sells applications with a price floor, means that there isn't a true market equilibrium and therefore consumer surplus has been taken away by producers.