I'm completely disgusted by Apple's behaviour on this topic. Apple should be ashamed of itself for gouging developers. This is like if someone has a bakery in Des Moines, IA and then wants to expand to New York, and the city of New York insists that the price of cake the bakery charges be the same or lower than the price in Des Moines where the rent and operation costs are a fraction of what they are in NYC. This kind of monopolistic behavior by Apple is worse than Microsoft at its worst in the 90s and the early 2000s.
Apple does not have a monopoly in mobile devices. Apple is acting as a distributor and asking for a cut for being that distributor. There are other equally viable distributors - web apps, Android, maybe even WP7.
I'm sure the Angry Birds or Pixelmator people don't begrudge Apple taking a cut for giving them a massive amount of marketing and promotion - as well as an ultra-simple way of receiving payment (still a major stumbling block in the online world).
The key thing is how they enforce the external restrictions. It does make sense to say you need to offer the same terms externally as inside the App Store - to the consumer. The problem is that this can appear totally unreasonable to the developer. It all depends on enforcement - if they go after 30% of Highrise revenue because 37Signals have a native client we will know things are wrong.
