As I understood it, the ransom is paid to God. When Adam and Eve sinned, they sinned against God. The blood sacrifice that cleansed those sins from the ledger would be paid to God, and he would then forgive the sin. That is how blood sacrifices worked in Israel, wasn't it?
I think the difficulty in explaining it, is that the concept is not very intuitive. Especially the part where the guilt for the sin is passed on to humanity, and the blood sacrifice therefore cleanses us of a sin we didn't commit, and doesn't redeem Adam and Eve. But it also wasn't a typical blood sacrifice, so the rules don't necessarily have to be the same.