I like going to http://www.wildlifebuyer.com/catalog.asp?catid=363&n=Exotics--Deer
and seeing what's listed and for how much. There are also several sites on Facebook that list exotics for what I think are pretty good prices. Seems like once a listing goes up, the person listing it will state that it's sold within a day or two, which tells me that the price was where it should be. Of course, some of the more rare animals list for crazy money, but then they seem to sell after awhile. $20,000 for a kudu bull and $25,000 for a ibex!!!!
Good luck, I'm still a couple years away from building my fence. I want to breed a few exotics with the hope of selling them to the big ranches.