I don't think that is quite accurate. Walmart is all about optimizing the the process of going from supplier to customer (reducing inventory help, optimizing shipping routes, etc). Apple is about controlling access to the suppliers.
Wal-Mart also guarantees scale when they negotiate to put something in their stores. It's what allows them to put downward pressure on their supply chain to lower their prices.
The logistics of getting the product efficiently to the shelves reduces waste by tracking exactly what sells geographically and why. The analogy breaks down on this since Apple is creating the end product, but the principle of getting preferred pricing due to scale is no different.
That's a part of it, but the biggest part is the deep discounts they get from suppliers due to the volumes they buy. No one else can get the prices they can and a lot of places end up basically supplying Walmart exclusively.
