Salah Times Pro has 870 euros MRR because of details the big apps get wrong: calculation methods per school of thought (configurable, explained in plain words), offline timetables for a full year, battery-friendly background updates, and a widget that respects quiet hours automatically during prayers.
General lesson for niche apps: the global competitor optimizes for the average user. You win by serving the specific user better than they can afford to. Every one-star review of the big app is your roadmap. I read 2,000 of them.
Monetization: one-time 4.99 plus a 9.99/year tier for families. The family tier was an accident (one email asking for it) and is now 40% of revenue.