These analogies are forgetting a big BIG piece of things. Payment is going THROUGH Apple (in your scenario Walmart). Any payment disputes, questions, refunds, whatever it takes time away from an APPLE representative. I have called them many times in the past many years about refunding app purchases and discuss some billing issues. I did NOT contact the developer's representatives. So yeah, who pays that Apple Rep's salary when they are focused on helping me refund WeirdCameraApp123?
So with your and others analogy, if you go THROUGH Walmart to purchase a TV show on Apple TV, and have issues with it not playing or whatever and want a refund, you will be talking to Walmart. So yes, I think its fair that Walmart gets a cut on the transaction.