Interesting that you're selling a GPL licensed app. I think that's actually quite viable in many cases. I'd rather pay a low price and get something in the app store than have to build it myself.
As much as I hate to say it as a developer: code is trivial. Finding users is the hard part.
Additionally, our long-term vision is to make the bulk of revenue from Teams subscriptions, where most value comes from a web-based dashboard (https://paretosecurity.com/teams), which is closed sourced.