My understanding was that the retailer margin was 50% and the distributor margin was 10%. So Apple/Steam/etc went "half of 60% is a great deal".
Of course the retailer margin is never actually 50%. That's theoretical if 100% of product is sold at MSRP. Actual retail margins are about 25% because of sales, write-offs, et cetera.
OTOH when there's a sale in Steam, they still get their full cut (of the reduced price).