As an ex-app-dev (failed), I can tell you it costs many tens of thousands $$ just to keep up with Apple OS updates, required coding changes, fix bugs and that's all before adding features. As @PeteBurgh says, it costs a fortune just to stand still. I gave up on my app as, despite good reviews, I could not generate enough revenue to cover the costs of regular updates. @darkroomapp is being honest and fair here IMHO. PS just downloaded Darkroom to try.