Nope. You made the assumption that the cost of goods sold was equal to their passthrough in IAP.
Which is true for apps. I'm an iOS App developer, and I get payments from Apple representing (roughly due to currency exchange rates) 70 cents for each of my my 0.99 apps and IAPs. And Apple's financials still show multiple Billions in profits and cash flow from the App store. This couldn't happen if their margin was only a few cents.