[ronsor]

Mostly Microsoft (inertia, you're already paying) and game consoles (expensive SDK/dev-kit licensing with NDA crap).

I see it less on Apple platforms except for published applications and niche tools.

[pjmlp]

There are many other computers out there.

You already paid for XCode via their beloved hardware margins.

[musicale]

What about that $99 yearly developer fee?

(Technically it is optional if you don't need to ship signed apps or submit to the app store and you don't care about the rest of Apple's developer program.)

[pjmlp]

That is on top, I guess.