First off, I've never heard of charging more for the head feathers. From my experience, there isn't much difference in mounting a Woodduck -VS- a Mallard, except for the thickness of their skin.
.#DraKE you are getting a Heck of a deal on those two birds if indeed the quality is there. Price isn't everything!
Alaska, I'm not sure what you were quoted on a price, but I heard everything costs more in Alaska. Around here $150 to $200 is the going rate for a duck sitting, flying, or with a crest. I personally like a pretty greenhead coming in to land with it's wings fully cupped.
Waylon, I think that the Merganser is the easiest duck to mount, and the Woody is the hardest based solely on the thickness of their skin, and the fleshing that follows. Nothing to do with their head crest. Just my opinion. Wings cupped, Pete-pec