That application is also probably not selling 100,000 units, so adjust your expectations downward accordingly.
Apple Watch app, widgets, Live Activities, new phone sizes... there are always things Apple wants you to add over time. Do you want meaningful updates or abandoned software? It doesn't take a full time job, but it's significantly more than $1 per install
Let me put it a different way.
You have already been paid everything you will ever get paid for work you did in 2021. Next year, I want you to do an unpredictable amount of work to support the 2025 iOS. How much will you charge me? Where will I get the money to pay you? Why would I spend it on this instead of something else where I might see a return?
I challenge you to demonstrate the Pomodoro app that has a full time dev effort for a year, and then requires anything more than piecemeal bug fixes or maybe a recompile in that four years of support...