I agree that Spotify is taking the right stance. In their position, working on whatever team is responsible for fighting Apple, I would also do anything in my power to fight. Having said this, Apple can do as they please. They control the hardware, the OS, the App Store, and the user accounts. The same was true of Twitter who effectively squeezed access to their API until one or two desktop clients remained. The only…
"Imagine if Spotify offered a lower rate for Android users... Wouldn't that send a very clear message to Apple?" - That is exactly what Spotify should do. They need to use the fact that Apple is married to its platform against them. Charge Apple users 12.99 and Android users 9.99 and then beat them by offering superior content. If Apple users want to sign up online then they can get the 9.99 price.
https://www.theverge.com/2015/7/8/8913105/spotify-apple-app-...