> What would be an anti-trust issue is if Walmart took steps to prevent their customers from shopping at Costco.

Apple is not preventing you from choosing to buy an Android phone.

Owning an iPhone is like being in a Walmart. You can either buy from the store or go somewhere else. Walmart-made products will be cheaper in the store. You can always go somewhere else. You can make the choice on whether you want to go to Walmart or Costco before, during, or after your stint in either.