Well, there is a simple way to test this... just get rid of the Patreon iOS app and just use a web version. Why does patreon need its own app? Why can't it just be web based?
I wish fewer companies had apps. I don't need an app for everything. I don't need every hotel I stay at to have their own app, I don't need an app to order food at a restaurant.
So why do companies make them? Because people spend more money when they can just use the in app purchase functionality. It is CLEARLY worth the 30% to most companies, because they keep pumping out single use apps that would be better as a mobile web page.