Re: Apples and Oranges
You're right about the important difference between Apple and Google. Apple are actively trying to keep their users secure, whereas Google look to be going through the motions a lot more. By making side-loading a lot harder Apple are also preventing their consumers from accessing cheaper (or more likely pirated) competition - but on the other hand that also means the consumers get better protection from malware and the app creators protection from being ripped off. Hence Apple consumers tend to get the best access to apps - so you've got ammunition for the walled garden versus freedom argument right there.
But on discounts for big producers you've got it a bit wrong. If I'm Epic and Fortnite is getting downloaded millions of times, then Apple's costs are going to be lower, because they only have to manually check the app once. Which is a much bigger cost than the data for each individual download. So you're not so much punishing the smaller developers, as aligning the price to the developers with the costs they cause. Which is what you'd exepct to happen in a properly functioning market.
The market failure here isn't amongst app developers, it's that smartphone OSes have become a duopoly. Worse, Microsoft didn't sell PC hardware and generally didn't take a cut of software sales, except where they sold their own. Obviously you got some dodgy competitive practises with MS Office, but not really with games and lots of other software.
In Apple's case, they run the hardware, so are less interested in data-harvesting and their app store cut also acts to help the app writers - since they try to block side loading for normal users. I know there's a way to get corporate apps onto iPhones.
Google at least allow sideloading. But that doesn't help app writers so much, as it's allowed a lot more piracy. And of course malware.
These markets probably can't be made to function properly at this point without government intervention. Which might well create problems all of its own.