I think a lot depends on your region. I live in upper Michigan, which has been in an economic downturn since the Great Depression so prices are lower here than in other places. I go to local fur and feather swaps and look around to set my prices. I can sometimes get a little more if I have printed signs identifying the breed/breed-combination of the birds for sale.
A lot depends on what it is you want in ducks--- if you are set on certain breeds, or if price is a strong consideration. If there are fur and feather swaps in your area, you might go to one in order to find something you like in your price range, it's easier than going around to different breeders and dickering over prices.