The cost of distribution is the cost of selling their commercial digital services on Apple's platform. If Spotify deems 30%/15% split is too much to be able to

The cost of distribution is the cost of selling their commercial digital services on Apple's platform. If Spotify deems 30%/15% split is too much to be able to sell their services on iOS, they don't need to participate in that market, they can continue selling their online streaming services on the Web and Android and and spend the money they would've paid Apple in distribution costs in more advertising/marketing to acquire new Customers. If the App Store revenue share is so lucrative they can also consider that as an opportunity and are free to build and sell on their own platform, invest their resources in building hardware + mobile devices, OS, Apps + software, dev tools, distribution channels, retail stores, marketing/advertising to entice everyone to use it and enjoy the 30%/15% revenue share from everyone else choosing to participate and thrive on it. Or maybe it will end up being cheaper for them and they'll get more revenue because of iOS's larger and quality user base to just pay the App Store fees for being able to offer their commercial services to the iOS ecosystem created with Apple's investments.