I suppose that would only happen if Apple were very uncompetitive in price. In the example above, the options would be equivalent to the company if Apple only dropped their cut to 25% and the competition was free.
Assume Apple dropped to 15% and the competition was 10% - then it would be 9.99 IAP, 9.63 on Amaozon/Stripe/Netflix, which probably wouldn't be worth the consumer confusion.
A micropayment is 5% + $0.09. For a $0.99 purchase, this is about 15%.
I would expect other payment processors to be similar.
This also leads to the question of "how do you maintain the in app purchases?" Is it an account on a website that has 100% uptime? Does it work for solo games when there's no network connectivity?
This works for Epic (big company, lots of payment processing already). It doesn't work for SmallGamerInc that would find that they'd need to do a bunch of other stuff to get it working that incurs more costs than what Apple offers.
Assume Apple dropped to 15% and the competition was 10% - then it would be 9.99 IAP, 9.63 on Amaozon/Stripe/Netflix, which probably wouldn't be worth the consumer confusion.