[iNate2000]

But Walmart wouldn’t let a vendor set up a kiosk in the middle of the store and accept payments with a Square reader on a phone, would they?

[horsawlarway]

Walmart has already purchased the items they're selling in their stores - in most situations.

That's how distributers work - They purchase an order of items up front and then sell them at a price point of their choosing.

Not to mention - In the walmart case, the user is free to go shop at safeway/publix/kroger/target/etc if they want. Where as with Apple you can only shop at the company store.