I have an iOS glitch camera app making around $500/mo most months https://itunes.apple.com/app/defqt/id817026377 - app is featured in some China photography lists and Apple recently requested promo assets for a feature, although they have not featured it yet. The only marketing is on IG, just posting images from the app and from other Defqt users. Been in the app store since 2014. My main income is as a freelance iOS and Android app developer. It's really a niche app so unless we get featured by Apple it will stay small. Ranking in the app store is a nightmare and outside of spending your way into rankings, you are left with the coveted Gold Standard of getting Editor's Pick from the Cupertino gang.