I wouldn't worry - there are some customers you don't want (and that's fine). Apps require a fair bit of upkeep and I imagine a camera app will need testing/modifying to ensure it works with the camera in every annual phone release. If you want to capture people who don't want a subscription add a lifetime plan 2-3x the annual price. Almost nobody will buy it. People complain about subscriptions but back in the day the number of people that complained when an app with 99¢ and not free was also staggering.