Firstly, that's not Apple paying income tax, that's their employees.
Secondly, they don't pay much in the way of corporation or other taxes that usually apply because of a sweetheart deal (Google also has one IIRC), which is why much of the EU is up in arms about the Irish government's behaviour here, that effectively allows these multinationals to operate across the EU without paying the usual expected taxes, giving them an advantage over local businesses and depriving governments of income, and there have been various court cases about it.
