As others have said, no, Apple does not charge you at the expense of the developer.
They earn their money through 30% of the shares they hold for selling paid apps. Free apps do not make immediate money for them, but are still valuable to Apple because they make the App Store more attractive (do you like to go to a store that has only a few items in the window?). This allows users to register the App Store more often than using only paid applications, and sometimes they also buy something, even if they donβt visit the App Store with this intention.
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