B is also one click, considering Stripe and others already offer Apple Pay as a payment option.

For C, customers can choose to continue using Apple's subscription management if they think it's worth the 30% premium that Apple charges. Or Apple could reduce the price to something more reasonable (Stripe Billing offers a similar feature set and costs 0.7%).

C is my biggest reason I'm not looking forward to these changes.

I love having a single dashboard for all my subscriptions and having an easy way to cancel them.

Now calculate the drop off every time someone saw the prompt: “Please confirm your Apple ID password.”

I’m sure it’s substantial over the years. As for point C, I really don’t care, every monopoly has had at least some advantages. We could make this even better by giving Visa a monopoly and having them build a web portal.

b) Apple Pay on Stripe seems a pretty low friction experience for web purchases. My app has a "buy" button that pops up a Safari window with an Apple Pay button the user clicks. Sure, it's an extra click but I doubt it's a slam dunk that the extra click is going to consistently cut conversions by 15% (or 30% for big outfits.)