This is glaringly evident at the very least in the way Apple and Google (don't) apply app store review to their own apps, so I don't understand why you're being downvoted.
FWIW I think Apple's apps do actually go through review, but the issues that crop up (non-public API usage, etc.) get swept under the rug (don't quote me on that though). Similar to how third parties blessed for private API usage probably get their apps through review.
The amount of commission that Apple receives from an IAP isn't something that's in the code for an app. It's not something that could be part of the app review process. It's an arrangement between Apple and the developer.
