Does Amazon or Ebay pays a fee after their each sell through their apps?

Please read the review guidelines, because they specify what you must and must not use StoreKit (Apple's in app purchase) mechanism for.

If you use StoreKit, Apple's fees apply to those transactions.

If you don't use StoreKit, then the rules and mechanisms for whatever you're using apply.

When you buy something on e-Bay, you don't pay with your iTunes account.

Thank you for the quick answer!

After you advised, I read those guidelines, but stuck again and still have a question, maybe you can help.

My dilemma: the site we are working on is actually selling credits, which can be used for purchasing videos on the site (or app, we are launching both).

So my question is: are these credits define as consumable, and we must use StoreKit? (hint: we do not want to use any in-app purchase)

Maybe there is no answer, but if there is any information on this matter, link it please, I have not found it yet.

Thanks!

The credits are consumables. You may need to create some way in which the purchased content is restoreable to other devices owned by the same user. Even though restoring is not required for consumables, the content that the credits purchase is not really a consumable and should be restoreable.

Your app needs to follow 3.1.1 - if you are unlocking code distributed by Apple in the app itself you must use IAP. You may be able to operate under 3.1.3 and not use IAP.