As I posted previously in that other thread, there are a number of different issues and by confusing them Apple is able to act anticompetitively while convincing people that analogies like yours are appropriate.
The issues break down something like this (in my mind):
1. Should Apple have some form of license fee for iOS SDKs and technologies?
- I think the answer to this is yes, but Apple acts like the answer is both yes and no, because they have so many inconsistent rules on this, if Apple wants to be a fair and equal platform on which apps compete fairly they have to charge everyone the same license fee structure rather than carve out exceptions for particular app categories (Reader apps, apps for purchasing real world goods and services)
2. Does Apple deserve a share of all revenue that occurs on iOS?
- Apple, again, acts like the answer here is yes for some apps and no for others based on which apps they can bully.
- I think the answer for this one should be no.
- If the answer was yes, and we take it to its actual logical conclusion, then all revenue from purchases made in safari should also count.
3. How should Apple be generate the revenue to cover the costs of running the App Store?
- If Apple has a large enough universal fee for accessing the iOS SDK then they can roll the cost of running the store into that.
- However if they want to make the fee smaller (or zero) they could have some sort of annual hosting and review cost based on the number of installs - Similar to CTF but more targeted towards recouping the costs of running the store - it would also have to be more universal than the current fee structure is as well.
Many people in this and other threads, as well as Apple, want to merge issues 1 and 2 together which I disagree with as it only makes things confusing and makes it hard to understand how Apple is behaving anti-competitively.
In your analogy, the membership would be issue 1 above but also reaching outside of the store into the home after the purchase has been made to demand further fees if you happen to use the thing you brought home from the store to make further purchases is issue 2. Again, what Apple is asking for is like buying a laptop at Costco and then Costco expects to be able to get a share of all purchases you make using the laptop.
Apple is acting like the Spotify being unable to add their own in app purchases system is like issue 1 when in fact it is issue 2.
Aside: This is not security, apps for purchasing real world goods already let you use alternative payment systems right in the app, Stripe has a whole SDK for it. If these apps are allowed then security argument is just empty words.
Apple charges a percentage fee (I think its 12/27% right now) if you want to include your own in app purchase system for digital goods (an arbitrary and capricious distinction vs physical goods). Up until recent court rulings apps couldn't even include a link to their website to sign up.
I don't want Apple to post a link to a website to sign up for Apple Music, what I want is for Spotify to be able to use their own IAP system without paying a fee to Apple for a share of a transaction they have nothing to do with (just like countless physical goods apps do).
I have addressed the issue of the percentage of the fee being a platform access fee above.