10% Sounds low. I can't judge for the product in question but for my programs, they are usually tiny blips standing on the shoulder of giants (libraries). So far i have never ask for money, if i'd do so i maybe would need to pass on 80% to not feel bad about it..

Not sure if you are cynical of sincere, either way, if the library devs get 47 cent from every donation driven program that relies on them, this could add up to some nice sum.