That being said, worldwide Apple only has 20% of the market now so while the average user is cheaper, there are quite a bit more users. That's probably why ad-based monetization also works a lot better on Android (more users).
[1] https://www.statista.com/statistics/951537/worldwide-average...
People who choose the cheap option really don't do much discretionary spending, people with iPhones actually make up the majority of revenue for many apps.
When you're looking for a "Todo" app, there's 1000's on Android, and many or most are free. Many people might be better served by a quality app, but when the alternatives are good enough, it's a hard sell.
> When you're looking for a "Todo" app, there's 1000's on Android, and many or most are free.
There are also a massive number of "Todo" apps on the Apple app store. Searching for numbers online seems to indicate that there are about 50% more apps total on the Google play store than the Apple app store, but for the more common use cases that still means massive numbers of choices on each store, both free and paid.