Kudos for being the only person on the thread to try to actually
answer the OP's question.
I was interested in this question also and I thought the entire thread would go by without anyone even making an attempt at an answer. It would still be nice to know exactly why Apple charges what they do though. I am certain that they must have reasons (at least in their own minds), as to why they charge more and it would be nice to know what they are. At least you approached the question logically and tried to think about it.
I am constantly under-whelmed by the "support" offered by this forum to people asking questions like this. I have started a few threads myself with reasonable well-thought out questions that either fall totally flat or merely attract a bitch-fight over some tertiary issue.
It often seems like these forums are a better place for a fight than they are for support of any kind.