Not only that, the data for those apps are on a remote server that is accessible via any other platform. Even when an app uses the standard file picker, you can choose any installed cloud storage device to save and load files - ie iCloud, Dropbox, Google Drive etc.
But the money they make on ads in the App Store has to pale in comparison to how much they get from Google
Now there must be more but $99 * 20 million is not nothing in annual revenue which is mostly profit.
If you have a company with 100 iOS developers, you only need to pay for one account that has permission to submit an app.
If you are exclusively a Mac developer, you don’t have to pay anything unless you are submitting to the Mac App Store.
A “registered developer” is not necessarily a “paying developer”, you can register as a developer to get documentation etc.
If you are working for a company creating an app, not all developers need to pay to publish an app. Also Mac developers don’t pay to distribute an app.
What the heck is a nothingburger?
Most of the money Apple gets from the App Store is from pay to win games - north of 80%. It came out in the Epic Trial.
Apple doesn’t really care if your banking app is a website or an app. They don’t make money either way.
Most apps on the App Store that could be a web app don’t charge users.