I'd be interested in getting paid by usage rather than once upfront. And if a free trial period let people get on board that would be fine with me. I have an a

I'd be interested in getting paid by usage rather than once upfront. And if a free trial period let people get on board that would be fine with me. I have an app that is "expensive" ($15) but I have dedicated users who paid once four years ago and continue to use the app today. All the major updates since have been free. While I don't know whether the pay-by-usage model would be financially better for me, I'd be pretty open minded about it and wouldn't mind the free trial.