Microsoft didn't have a monopoly on computers, yet it was guilty of pushing all their users to use their apps over others.

Apple and Google are the only major phone OS's. If they control what you can install on your phone, they have a monopoly.

> Wallmart choose their suppliers, and sets the markup, why can't Apple?

You're really comparing setting up a physical store to building world class operating system and phones? Almost anyone can set up shop and start selling things that Walmart isn't, or from suppliers who won't deal with Walmart, but it's not how tech worms. You're living in a different reality.