I think a lot of people wonder about selling feathers, so I think it's worth asking.
First of all, not all states allow the sale of wild game feathers. If your state does, then expect lots of feathers to be on the market...in other words, you won't get much from an experienced buyer. You will get more for fully process feathers of the highest quality. By fully processed I mean, washed, steamed, hand selected for perfect vanes, and with the entire quill intact. If you cut and grind them into popular shapes, you can get more. Again, many people are doing this so don't expect too much.
The most profitable feathers seem to be those from rare breed turkeys that are bred specifically to produce raptor-like feathers. There are some turkeys that produce feathers that look like eagle, crow, and buzzard feathers.
A quick tour of ebay will give you a good idea as well.