> This is similar to what Wix requires when you develop for their platform. Wix requires developers to profit share 20% of your revenue for any customers that j

> This is similar to what Wix requires when you develop for their platform. Wix requires developers to profit share 20% of your revenue for any customers that just so happen to use the part of your app that communicates with Wix. As you have described the Wix situation, it is not analogous. Apple only gets a share of revenue that they originate (user creates an account using in app purchase). Apple does not receive any revenue from users who sign up elsewhere and sign into their account in the app using their already extant account.