Many thanks but Apple do not make money from apps I believe.
The company or person who developed the app makes the money, but they should as they invested time and money developing the app
So many things to catch up on in this thread, sorry for late arrival.

The way it works is, the developer names the price for an App (from various price tiers). I can choose any tier I like, it's my choice - but obviously the higher the price, the less sales volume I might get. But no matter how much or how little I choose, Apple take their percentage. I forget the legal terminology, but they are acting as a kind of sales agent, collecting commission.
Also, the developer pays $100 a year developer's program membership fee, which entitles him/her to run test Apps on real devices, and publish the Apps on the App Store.
I hasten to confess, none of my Apps have ever made more than peanuts. I think that is the same for vast majority of dev's, certainly since the 'gold rush' of the first few years of the App Store. Unfortunately The T&C of the developer agreement actually forbids me from going in to any great detail, even if detail that might be readily available from searching the web. But that's basically how it works. Hope nobody from Apple, reading this, decides I've already said too much.

If you have a MAC and fancy having a go, you can download and install the SDKs for free. But you won't be able to run on on real devices, just the simulators.