Why do you (or whomever "we believe" refers to) think Apple's commission for IAP made using other payment methods will only be 10% (as compared to 30%)? I would expect that commission to be much higher - something like 20 to 25%, possibly even closer to 30%. That is to say, I think it would be higher than 10% unless some change was made to federal law which abrogated intellectual property rights in a way that limited what Apple and similarly situated others could charge for the use of their intellectual property. I haven't thus far seen where such a change has been proposed.
In-large-part because Google is ahead the curve here, & they decided to go with 11%.
That happened ONLY 1-2 months ago.
If Apple, OR Google, decides to go much higher, the "Trust Busting" efforts will never stop !
That's the main reason I believe they "can't & won't" go higher.
Also, look how fast Tim Cook is aging right now !
You think he wants another few years of this ?