Caribou mounts are pretty common. Unless it is a huge bull that will place high in the record books you'll be lucky to get $350 out of it. The problem with selling trophies is that, with a few exceptions, they only have value to the person that did the hunting. Some examples of exceptions are the real oddities like Takin, Siaga , a really big mulie or things no longer hunted like Guar and Hirola antelope. You could pretty much set your own price on those. But caribou are still wildly available to most hunters.