Third-party billing was one of the primary points of contention in Apple’s lawsuit with Epic Games, which is currently being appealed. Epic wanted the ability to point users playing Fortnite on iPhones to the Epic website to buy in-game currency inside the app. That violated Apple’s rules and bypassed Apple’s commission.
Link: Apple opens up third-party app payments in Korea, will still take 26% cut
via http://www.cnbc.com