If you're running a brick and mortar book store, payroll would unlikely be 70%. Payroll would be your highest cost but it should be 30% on the high end.
If we want to try and analyze this, we should analyze what music distribution was like prior to digital. My guess is that for most artist who went through traditional publishing and distribution, they only received 10-20% per album sale. That seems high too.
I should have been clearer, I used 70% of revenue because that is what Spotify gives to artists. Of course, software can do that as it scale infinitely, retail cannot. I can't tell if 70% is generous or not -- many independent artists think it isn't.
If we want to try and analyze this, we should analyze what music distribution was like prior to digital. My guess is that for most artist who went through traditional publishing and distribution, they only received 10-20% per album sale. That seems high too.