I feel like 30% works for one-time purchases between $1-10. Which is what I figure most Apple App Store apps go for. No matter how you cut it you're still going to pay credit card transaction fees. Most of the PC games are likely between $10-60, where 30% makes less sense (the marginal bandwidth, storage, etc isn't that much more expensive).
However, digital platforms like Apple's are a now a lot more mature and have reached a scale where the costs should be coming down. I've been wishing for decades that credit card fees would go down.
- Epic Games refused to release Fortnite via the Play Store
- Valve lowered it's cut from 30% for major publishers to keep them from leaving
- Epic Games then announced a store with a 12% cut for PC and Android (the latter coming in 2019)
- Discord followed by announcing a 10% cut
- Netflix has pulled out of paying Apple's 30% cut
- There's a pending antitrust case against Apple's Store that has, on procedural grounds, already made it to the Supreme Court