I am just guessing, but it would seem that the promotions are only available on European connecting itineraries, e.g. MAD-AMS-HEL or GVA-AMS-STO. That would mean that CDG-DUS will cost more than say MAN-CDG-DUS. I noticed that other nonstop destinations from CDG or AMS priced out at the normal price.
Is this reasonable, or madness? Do my suppositions have any basis in fact?