I made an antler pen on special order for the membership to give to the outgoing long-time president of a local conservation club. I did the pen free with antler stock provided, there was enough left over for three more pens. After that three more members came to me with antler to trade for pens. I ended up with lots of antler. I'm making lots of pens but not selling much yet.
I've made Atlas, Sierras, slims, euros, even one cigar and I'm going to try to sell them for $30-$60. I sold a euro pen/pencil set in a hand made box with the bark still on it for $100, the box took a lot more time to make than the pens.
The thing about antler pens is that they either love them or hate them. Some people are disgusted by the irregular colors, the thought of the source, the whole idea of hunting, etc. Others love them and would be willing to pay a lot. I think hunters and outdoor types are willing to spend more for antler than for wood or acrylic of the same pen style. Don't be suprised if some people think they are worthless, and don't be suprised if the hunters want to trade antler for a pen; I could accumulate a garage full of antler before I sell anything.