And I don't, tbh, have an opinion about the rest of your post; I'm talking about Steam, not Apple.
But, having gone down this road myself (and why I cite the Jeff Vogel talk): you would almost certainly spend more than 30% on customer support and payment processing and fraud protection and accounting. Or you would do it incorrectly, which is worse. And, regardless, you'd expose yourself to a way smaller audience. It seems to me to be a good way to shoot yourself in the foot for no gain (and as an app developer myself I certainly wouldn't bother).
And I don't, tbh, have an opinion about the rest of your post; I'm talking about Steam, not Apple.
But, having gone down this road myself (and why I cite the Jeff Vogel talk): you would almost certainly spend more than 30% on customer support and payment processing and fraud protection and accounting. Or you would do it incorrectly, which is worse. And, regardless, you'd expose yourself to a way smaller audience. It seems to me to be a good way to shoot yourself in the foot for no gain (and as an app developer myself I certainly wouldn't bother).