alt Hacker NewsI think the less frowned upon way to charge is to just do it once.
If the Apple store supports this, free trial + one time payment sounds like a good way. Don't optimize for freeloaders, as someone else said.
If the app relies only on iPhone hardware and/or is not a live service, an account/subscription should not be required. Even non-devs might justifiably ask "why do I need a subscription for a camera app".
Halide asks for a subscription. Not entirely sure why yet. Yes, it is more advanced than the normal app. Also slower and I haven’t noticed any changes or improvements in the last two years. Maybe support for new features in newer iPhones.