But just like my TV and my desktop computer, I've paid for my phone with cash. Its mine. Just like my PC, I don't owe Apple Computers any extra money in exchange for the privilege to install apps like spotify on my device. The benefit of having access to the app store is already factored into the (quite high) price I paid for my phone.

And if you can find a way to defeat it's security, you are free to do so. However being incredibly locked down and secure is one the the product's features. It's up to you if you still want the product, but that's how it comes.

True, but a counter argument could be that Apple has created the ability of your phone to have apps installed on it. And I’m theory you could jailbreak your phone and install any app you’d want.

Sure; but I paid $1000 for my phone in part because of that capability. My phone would be worth less if I couldn't install apps like spotify. And unlike a game console, app purchases aren't used to subsidise the phones. Its pure profit for apple.

And I wouldn't have a problem with that in general, except it feels dirty to claim Apple are saints for graciously allowing apps like spotify to be sold on their platform. They're already being paid for doing so through phone sales. Leveraging the monopoly they hold over the ios app store against Spotify, one of their competitors, is exactly what antitrust legislation is designed to prevent.

And the developers are paying a fee every year just to exist on the app store.