I think YetAnotherNick means the actual words "30% Apple Tax" on the screen.

I don't see how that's possible from his comment:

> If you don't know that, it is not allowed to sell for more in iOS than in your site, and the app will get banned for attempting that

He seems to believe that Apple explicitly bans apps from charging more for iOS subscriptions / IAPs than they do elsewhere (e.g. purchasing the subscription on their website), but I can find no evidence to support this, and a lot of evidence to the contrary.

They do so implicit, then moment is visible to the user that they can buy thinking cheaper elsewhere Apple will cause trouble.

I.e. you are not allowed to be transparent with pricing.

This is literally not true: https://news.ycombinator.com/item?id=24239143

No it is, you are allowed to sell for more but you are not allowed to be transparent about it.