> If you have a complete billing system outside of the app and the user can never get to a page with signup or billing information from inside the app, then you can still avoid having to pay 30%.

I'm quoting [1], but from my expirience that's true, the problem comes when you link to your website without giving the option to pay with Apple system. Slack doesn't have any direct link to add seats, I think that's how they avoid the 30%.

Why Spotify wouldn't do the same then ? I think maybe because they target a more mainstream public that will not understand that they have to go to website to pay and then go back to the app? Maybe they reckon that would be losing more than 30% without that flow, or I'm missing something.

[1]https://www.quora.com/How-does-Apple-determine-whether-a-ser...