The key thing is that the codeshare marketer can only sell the inventory access to which they've been granted, at an agreed markup to the wholesale price, whereas the operator marketer can move its prices up and down at will, including taking and giving back markup over cost. This can result in the codeshare marketer being more expensive as it has access only to a more expensive fare class or doesn't get the immediate benefit of a cut in pricing by the operator, but it can also result in it being cheaper, as the inventory sharing arrangement can delay the pass-through of a fare increase by the operator or (less often) result in the operator having sold out of its reserved portion of a less expensive fare class while the codeshare partner still has rights to its allocation of the less expensive fare class.