Hi! I'm the solo developer of TigYog.app. I've been working with Andrew to build out the course. What percentage would you consider appropriate? It's set at 20% essentially because I have rent and bills to pay :-)
I wondered how the creator of this course could guarantee the course would be available forever, and what a headache it must be to continue to maintain the hosting/content if sales taper off. Outsourcing that job to a service which is hosting many such courses (and with new ones continually added) makes a lot more sense here, and of course you have bills to pay too. That 20% commission isn't just covering the cost of time you put into the course builder and hosting now, it covers hosting in perpetuity.