Software is 100% margins. How is it despicable that the party that originates the sale gets a share of the proceeds? Apple doesn’t get anything if Microsoft originates the sale on their own properties and the user simply enters their username and password. Getting paid for enabling the sale of goods and services is a completely normal thing in all aspects of business.
It looks like MS just swallows the extra cost given that Microsoft 365 Family costs the same $9.99 from the iOS app and directly from the website.