

Well, they do provide the AppStore and the whole underlying infrastructure. So a fee in and off itself is not unreasonable.
However, since the AppStore is the only channel for selling/downloading apps it reeks of monopoly (which Apple is rightly being investigated for).
Basically all illegal drugs started as legal drugs aka medicine (Opium, Morphine, Heroin, etc). The distinction is a relatively recent development. Even today a drug store is a reputable business. A drug den not so much.