At a certain point, if you execute so much better than the competition and set yourself up differently (controlling and innovating in hardware too) and you maintain total control of your platform, you can dominate in the market to such an extent that you have a virtual monopoly.
Yes, but Apple do not have a monopoly in smartphones or computers. Maybe, just maybe you could say they have significant market dominance of mp3 player market, but who cares about that.
