B-Boy, no, I don't do this professionally. I'm basically a hobbiest. I mount birds for myself and relatives and friends. I particularly like doing them for the kids of friends of mine. The are really amazed by the whole idea. I just did a pheasant for a friend's son that was his first bird. It really came out pretty good. That little kid's face really lit up when I gave it to him.
Given the amount of work I suspect is involved, $250 a bird certainly doesn't seem out of line.
Skeeter, $250 a bird is on the inexpensive side, especially whe it comes to waterfowl. But, it really isn't a lot of work. Or even materials. That pheasant I did took about 3 hours total. and that includes all the fiddling as it was drying and putting the finishing touches on the habitat base. A duck might take an extra hour. They're a little more difficult to flesh and take a lot of cleaning with degreaser, but the habitat is usually just a piece of drift wood and a hanger loop. As far as materials, with today's prices, you're looking at maybe $10 to $12.
Still, on a professional basis, $60 to $70 an hour is cheap.