Apple actually doesn’t charge a fee for this. You can build an app in Xcode and install it on your own device. You can’t distribute that app publicly though.
> G execs were in the position of having to buy off people
There’s your answer - having a monopoly is not problem, abusing it is.
But tying (e.g. of an app store to a platform) is classic monopoly abuse.
Your interpretation on tying is not well aligned with usual legal interpretation. Unless the App Store is considered not to be a separate product (which had been Apple's argument for a long time on App Store and Safari by designating them as "system services of iOS"), this is clearly tying. The question is if Apple's current practice is illegal tying or not. Whether the customer wants it or not is not important here; you can give them freely to gain market dominance then reap profits later on whenever the competitors are all gone.
MS actually doesn't have a good argument there, so they decided to unbundle it.
It's a separate question if Apple has been monopolistic or abusive with the terms of that app store, a question I couldn't possible judge; but the app store in and of itself isn't the problem.
Having a monopoly should be case enough.