FYI: Apple disallow you to redirect your users to subscribe outside of their app without their fee. You cannot tell your users "go to our website to subscribe by check for 30% less", that gets you banned. So yes, you are forced to use them.
> 3.1.1 In-App Purchase: If you want to unlock features or functionality within your app, (by way of example: subscriptions, in-game currencies, game levels, access to premium content, or unlocking a full version), you must use in-app purchase. Apps may not use their own mechanisms to unlock content or functionality, such as license keys, augmented reality markers, QR codes, etc. Apps and their metadata may not include buttons, external links, or other calls to action that direct customers to purchasing mechanisms other than in-app purchase.
Also, I don't know how common it is in the US but in the EU and here in France we have "prélèvement" (~bank direct debit ?)
Eg I (virtually, on my computer) sign an agreement for company X to take amount Y from my bank account every Z amount of time for a given service. It takes less than a minute to setup and sign directly on the provider website (no need to contact or connect to my bank).
I can cancel it at any time through the provider or at my bank.
Since a couple of years they are valid in the entire EU accross countries "prélèvement SEPA" (Single Euro Payments Area).
They're entirely free, for the customer AND the one billing them (there are bank fees depending on your bank, but no interchange fee, eg I use them to charge many of my customer and it costs me a flat fee of 25e/month for the web access).
That's how I pay my amazon prime, my amazon purchases, my electricity bill, my mobile phone bill, ... So a certain swedish music company could bill me in france that way for virtually no fee.