Just to emphasize your point, 30% take is relatively small in the retail world. A store like Amazon or Walmart or Target or Best Buy generally wants a cut of 40-50%, if not more. And that doesn’t include the cut many distributors want to take for being the middle person.

(Source: I’ve been on the executive team at startups with products sold in retail stores)

It's not even a valid comparison and disingenuous because software products now don't need to be sold through any retail outlet, and can be sold directly to the customer through the internet. There is absolutely no need of any app store as a middle man here.