A few comments:
1 - Your parent's anniversary is coming up. Being the classy lad that you are, you decide to get them gift cards to Olive Garden and Red Lobster (oooh, fancy). You can either go to each store individually, initiate a new purchase / credit card transaction, deal with the hassle of driving, etc. Or you can go to WalMart, while you're already shopping there, and pick up the gift cards at the counter. Wal-Mart isn't doing anything for the restaurants, right? So they shouldn't receive any cut, right?
Of course not. Because that's not how business works. If you're displaying in my store, I'm going to take a cut.
2 - To the people saying "30% is too much! Publishers can't live with those rates!" It's very easy to get around this. Just get people to go to your site and sign up.
What's that you say?
People will do it in IAP because it's easier, and they already have their credit card details?
You mean, there's value to the customer in doing it from within the App?
It's more convenient for the user?
THAT'S what you're paying the 30% for.
If you think that there's not a TON of impulse buying that happens on the App Store and iOS store... well, I'm not sure what to tell you
There's a value associated with that. Just like batteries, candy bars, and magazines pay more to get into the check-out aisles at supermarkets. That "impulse-buy" exposure is a valuable commodity. Apple wants paid for that, too. (Just like every other store in existence).
Finally, having something like IAP (as well as 1-click buying on Amazon) makes people much more likely to spend money. When you're not entering your card details (or forking over cash), people have a tendency to not think of it as "real" money. It's the same reason casinos use chips. If you can have people forget that they're spending money, it's a lot easier to get it out of them. Click...boom... bought.
All of these things have value.
Plus, Apple's handling the credit card processing.
Plus, Apple's handling the customer details.
Plus, Apple's providing the customer support for billing disputes.
Plus, Apple's providing advertising in the form of App Store placement.
Plus, Apple's providing the content provider placement in an exclusive searchable listing of "approved" apps.
Every single one of these things can (and should!) be monetized.
We'll see what the market really bears. But I have a feeling it's going to turn out like the initial complaining on here about the 30% App Store sales. Non-developers were on here, yelling and screaming about how Apple was being so unfair. While the experienced developers were sitting back and licking their lips in anticipation of the money that would come rolling in. And it did come rolling in.
The difference, of course, is that in this instance, you DO have some experienced developers/agencies saying that the fee is too high. We'll see soon how it shakes out. I _still_ think that it might just be a case of a few squeaky wheels. But I'm not firm enough in that assumption to say I'd be surprised if a LOT of content providers start pulling out.
I'm honestly now sure where I fall on this -- I think Apple is definitely due a decent cut of IAP, and I think the requirement of having things available in IAP (and the price matching) are all good things for customers. Maybe the 30% is too high.
One last thought:
70% of 10 sales is equal to 100% of 7 sales. That means you need to sell 43% more product to make up the different. Do I think the convenience of IAP makes it likely that a developer will see that 43% increase in sales quantity? I do, absolutely. And that makes the 30%-- no matter how much of a bitter pill to swallow it is-- a worthwhile inverstment.