Developers are not the only small businesses subject to Apple's 30% commission. Ebook publishers also have to pay the 30% commission to Apple for inclusion in Apple Books.
Then there are the indie musicians in Apple Music and indie video publishers in Apple TV. I don't know how much their rates are, but if it's anything like Spotify or Amazon Prime it's not much.
Will these other indie producers get a break too, or is it just developers?