Go on your local Craigslist and see what your local market is asking for them.
Organic verses nonorganic
Free range verse not also effect price. Since some won't let their ducks out of a pen ever, or only for an hour here or there, where others free range all day. We free range ours only going out to feed, change water and do lock ups daily. We will sit some days and watch the birds, but they are loose 12-14 hours a day truly free ranging.