Many on HN would say that Apple's 30% cut on App Store sales is perhaps unfair. Is Amazon's 75% or 60% unfair, or is it highway robbery? Not to mention what they actually pay instead of the contractual amount.
Yet in HN discussions, people seem far more inclined to defend Amazon's practices than Apple's. I wonder whether the reason is that a lot more of them make their living off writing software than off publishing audiobooks (but maybe there is some other factor there that I'm missing).
[Disclosure: Apple employee & shareholder, not involved in store related activities, not speaking for Apple]