In March 2016 I started writing an Android app (
https://play.google.com/store/apps/details?id=com.unwrappeda... ). In May 2016 I released it. You can set wallpapers on Android with it. The last new wallpaper I put up was in November 2018. Early May 2019 was my last app update.
I did not run ads in 2018 until I ran <$15 worth in November-December. I ran ads one day in 2019 (the day of the last app update) and got less than 350 clicks on the ad. I have not run ads since.
So I have done nothing since early May 2019. From June 1st 2019 to Jan 31 2022 I made over $3500 on ads for it. It made $70 in October 2021, $87 in November 2021, $104 in December 2021 and $82 last month. In March 2020 it made $264, then $242 in April 2020, then $264 in May 2020. This is from ads.
My expenses are a $10 a month Ramnode VPS, a $20 (probably overkill) a month Linode VPS, a yearly Namechap domain name expense of maybe $30 or so. It kind of pays for itself, plus a little more.
I could make more money on it with some work, or release another app, but my current direction is "those efforts would be better off trying to progress my career". Studying Kotlin helps me at my day job, but also could potentially help in the future if I decide to revisit the app.
I had another app which in late 2013 and early 2014 was making $2000 or more a month. My expenses were about the same, I ran no ads at that time.
> the effort is much greater than it sounds
The initial effort for both apps was a lot but then less work was needed to be done. I also learned how to put a whole "modern best practices" app together (plus the backend REST API, plus the relational database and its normalized schema etc.)
> was worth it after your initial effort and ongoing maintenance
For 2 1/2 years my ongoing maintenance has been next to nothing. I had nagios watching it while working on it, but a change on the nagios server broke nagios and I have not fixed that yet. Every once in a while I try the app out and see if it is working.
My Android (and Python REST API) skills are much better than they were when I wrote the app and if I released an app (or apps) now, I'm sure I could hit the $2000 a month mark again and then start pushing that up, even with existing competition. But I make multiples of that in my day job and with study can level up my title and get the pay that goes with it.
There are different motivations to do it or not do it which fluctuate with time. I could see going back to writing my own apps at some point.