It's exactly the same. Nike uses Footlocker's distribution (ie. lots of stores) and pays them 30-45% of the retail price. Apps use the Apple store in the exact same manner. Apple gets 30% for being the storefront.
I think the better wording of the original gripe of google not wanting to pay Apple would be: who in their right mind (who is fully capable of selling stuff online) would want to pay their competitor 30% to do the same thing). My rebuttal to that would be that google needs to pay apple 30% to get access to the other half of the population who does not have an android.