Cost of goods refers to the production cost of an individual item. COG for app store is zero. You don't even pay for hosting your app on the app store.
Software developers are R&D, not cost of goods.
There is R&D associated with Starbucks coffee as well (researching beans, refining the blends, etc), but nobody really factors that into its perceived value.
- If you include equipment, rent, and utilities in your cost calculations, then you have to include software developers and servers that are powering the app. I am not talking about apps that you build, publish and forget. Most apps have backend and engineers maintaining and supporting them.
- You ignored my point about the customer acquisition cost which is likely to be the biggest cost for most apps.