We went for a "pay what you want" model for my latest app. It's a real simple utility app but we were pleasantly surprised with what people paid. I gave a quick overview of all the numbers here https://medium.com/@reddavis/stand-app-9ee0fc3355c
This could be an idea.
Before every conversion (or daily) ask for a payment, which could be 0.
But without the possibility to make economical payments in the 10cent area this will not work.
Yeah, you'd basically need cash or cryptocurrency for that size of microtransaction (nanotransaction?). If I could pitch in 20-50 cents to a project I like in a few seconds, I would.