Sure I can understand that rationale, but freelance production is all feast or famine. I personally hate the idea of paying monthly for something I would be using sporadically. If I have a month of all post production or even worse a month with nothing $5 suddenly hurts a lot more because its not just your $5, its everyones together wanting me to pay you like your my employee every month. Why not partner with us instead of grabbing for the lose change in our wallets? Apps can have in app purchases. Why not an export fee instead of a monthly fee? Its much easier to wrap my head around a cost to complete single production with "this $5 will save me at least an hour"and simply paying you for the service you provide to each project.
Simply put I don't want to track my time and use of your app to ensure a subscription based model is worth it.