FWIW brick and mortar stores usually take 40%.
And that’s a big fraction of their services. https://www.thestreet.com/investing/google-pays-apple-billio... estimates that at $9.48 billion over 2018.
Downloadable is nominal outside of store. I had millions of downloads back in 2005 timeframe and we never even looked at file hosting cost.
retailers pay suppliers some wholesale cost for their goods. doesn’t seem like an analogous situation to a marketplace that takes a fixed cut of every sale.