The cost of a human working all day is negligible; they need a little bit of food. And yet they still expect to be paid - sometimes quite a lot.
Just based on your quote and without having much interest in the case... the fee isn't about covering costs. They have an app store, people want to be in the app store, and Apple is going to charge them a fee to be in the app store. Similar logic to drawing a wage.
This is bad analogy. A person who works provides services or labor worth a certain amount of value in exchange. Often that value exceeds the wage. For example, a software engineer $3000 "worth" of work in a day, but only gets paid around $1000 for that day. I understand the worth/value is a difficult thing to measure.
So Apple is more like the Mafia. The threaten negative/adverse action, if you don't pay them.
Also, historically, software could be installed on computers without the permission of an overlord. I'm aware iOS & game consoles are glaring exceptions.
I see the argument that people should be allowed to install whatever they like on their phones as very strong. However that has nothing to do with Apple's fees, costs or value add. It might seem pedantic, but the separation of value and cost is fundamental to how everyone improves their material wellbeing and needs to be protected.
And the argument that Apple is like the Mafia because they can exclude you from something would cast most businesses and all landlords as Mafia-like. That is a position some people hold, but if mafiadom is so embedded and accepted in society it undermines the idea that Apple's is a unique problem and that it will be acted on.
My main point is: on a desktop/laptop personal computer, you can install software without any overlord's permission. On iOS, you can't. That's seriously messed up, and wrong. And, yes, a lot of business (and landlords) are Mafia like. I'm hoping for a strong left-wing party to come into power in the future, and completely turn this upside down.
Just based on your quote and without having much interest in the case... the fee isn't about covering costs. They have an app store, people want to be in the app store, and Apple is going to charge them a fee to be in the app store. Similar logic to drawing a wage.