Comment by inputmice

Author here: Indeed, 15% is fine. They do provide some services. They provide the CDN for downloading the APK. They handle sales taxes in the various countries, which would be a PITA to handle yourself. Similar-ish services like Patreon charge a fee too. The 30% they charged a couple of years back was bad. But I could live with 15% if the support were anything other than zero.