It's entirely relevant. That 30% pays the costs of the app store, and bandwidth is probably the biggest cost of running the app store.
Please show me where Apple says the $99 I pay every year pays for their Sales, Marketing, Distribution and Operating costs of running the app store and getting me customers.
Please show me where Apple says the $99 I pay every year pays for their Sales, Marketing, Distribution and Operating costs of running the app store and getting me customers.