So is 30% unreasonable? I don't know.
I do. 30% is very reasonable, for what a developer gets in return. But that's not the issue here.
The issue is that a developer has no choice but to pay that 30%. If a developer want to use a competing app store to put apps on a iPhone, run a competing app store themselves, or do similar with a different pay system, then they can't. They are forced to pay that 30% or forgo the customers they might reach.
Ultimately though, the customers of the developers are themselves forced to pay that 30% (because the customer always pays in the end). They cannot choose a different app store or payment system, not even an in-app store and payment system. This is anti competitive, reducing consumer choice, increasing consumer pricing. It is a known that like for like app prices are higher on an iPhone, with less free apps available.
Apple tried to argue that this case should be heard in American courts alone. As if Australian consumers are somehow not protected by our own laws. We have rather good pro-consumer laws here in Australia, and Epic might actually have a decent chance of winning.