I would love to hear your experiences if you made money by selling or making iOS apps
Last but not how much time you spent acquiring skills to build iOS apps as I plan to get into it
I think the experience varies depending on the type of app you're building. It would be much more useful to address a narrower question. What type of app? How do you monetize it, etc?
I haven't personally launched an iOS app yet but according to CNBC the App Store had a gross earnings of around $64 Billion last year. https://www.cnbc.com/2021/01/08/apples-app-store-had-gross-sales-around-64-billion-in-2020.html
If you can find a problem with demand and it best suits the iOS platform, then you could have something great on your hands.