Invisible to the customer is the fee apple takes when purchasing in the app store or a subscription within an app.
The music-streaming service filed an European Union antitrust complaint on Monday night alleging that the maker has behaved unlawfully and abused its dominance in its App Store to favour the company's own rival Apple Music service.
It's why, after careful consideration, Spotify has filed a complaint against Apple with the European Commission (EC), the regulatory body responsible for keeping competition fair and nondiscriminatory. Spotify no longer allows users to subscribe directly through iOS - and Apple's policies prevent the company from telling users how to subscribe through other portals. Before it stopped selling Premium subscriptions through the App Store in 2016, it had one of the highest-grossing apps in the US and around the world.
Horacio Gutierrez, Spotify's general counsel, said the company was pressured into using the billing system in 2014, but then was forced to raise the monthly fee of its premium service from 9.99 to 12.99 euros, just as Apple Music launched at Spotify's initial 9.99 price.
Apple has been kicking music-streaming service Spotify around for years, and Spotify is fed up. Spotify also accuses Apple of blocking upgrades or disrupting the Spotify app's function on Apple services in return for not using the payment system.
How Apple handles that dual role of gatekeeper to iOS and also an app and services provider is part of Spotify's justification for its complaint to the European Commission (EC), according to the firm.
Many of those who do continue to sell subscriptions and items through the App Store tend to charge more for them to make up for Apple's cut. And Ek says that all app stores should not be allowed to control communications, including marketing and promotions, between services like Spotify and its customers.
Spotify has filed a legal complaint against Apple for what it believes is anti-competitive behavior.
One example that Ek outlined in his written deposition, is the manner in which Apple taxes businesses that want to use their platform as a seller's market.
"We aren't seeking special treatment", he said in a blog post. He emphasized that Apple requires Spotify and other digital services to pay a 30 percent tax on purchases made through Apple's payment system.
Ek says that Spotify wants the same treatment as other App Store apps like Uber and Deliveroo, "who aren't subject to the Apple tax and therefore don't have the same restrictions". "And to keep our price competitive for our customers, that isn't something we can do", he said. That's what competition on the merits is all about.