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.
If you don't like it, please, tell Apple (or Google) that bandwidth has to be paid.
Until then, it is irrelevant if the app is 10kb or it is downloaded 12.000.000.000 times.