Thank you for your clear and informative reply.
For the benefit of everyone interested in fees I'd rather share it here as a theoretical scenario.
I made a mistake in the initial calculation, the actual payment processing and transfer fees vary between 8-12% of gross revenue so it averages to 10%.
So in my case the works I'm selling range between 10 and 20 USD in price and typical payouts range from 200 to 400 USD. Payment processing fees account for ~5% of the 10%.
This leaves another 5% taken by transfer fees. Is there a resource or table I could use to calculate the transfer costs? I can see Payoneer/Paypal websites to learn about payment processing fees.