Thanks! Much appreciated.
Unfortunately I don't see how 20$ one time fee will works for such a niche app. After commissions and taxes $20 becomes $10.
Anywhere in the developed world the money required only to survive is at least 2000$, which means I will need to be selling 200 copies every month as long as the app exist only to get basic level of income and accumulating customers that I will have to support the years to come. What happens if the next year sales drop to 100 a month? It will become an abandonware and make me enemies or eat up all my time for nothing. Many years ago I purchased Halide and later it become a subscription app, I felt deceived and still hold grudge and I don't want to be that guy. It's subscriptions right away and have only the people who think that 2$ a month is a fair compensation for the service.
One time payment is either paying for abandonware, charity or scam.
With subscriptions, it's a service. It's the best for everyone. Some people associate it with greed but I don't agree that expecting getting paid for work is greedy.