That’s a big cut, but it’s not exactly the same, because (for an example) credit card companies don’t have an automated and actual human team evaluating safety of and legitimacy for products sold.
The 30% fee is cromulent when it's stuff that's clearly related to the app store activity. I'm not even that upset about charging a 30% fee on video game microtransactions. But the 30% fee is being charged on purchases made within app for content consumed outside of the app, which really starts to look a lot more like a 30% credit card transaction fee.
Neither does Apple. They have a "review" process, but that's a far cry from actually providing real indemnity, and if they dont do that then its not worth the cost.