Earlier quoted context omitted.
It's not their house. Someone bought an iPhone (not leased, bought, they own it now). Someone else made an app that that person wants to install on their iPhone (solely thanks to app developer's own marketing efforts). But Apple thinks it's appropriate to have their finger in the pie too.
Nobody bought the Apple SDKs or OS though and every app depends on them. I get people are use to free, but plenty of companies license software for royalties that does a lot less.
That's what the $99/year fee is for. Apple set that price themselves. It can also be argued that some of the cost of the SDKs is included into the price of the Mac that any iOS developer has to have.
> or OS
That's included into the price of every iPhone because you can't even buy an iPhone without an OS or install your own, like you can do with PCs.