Well here's a fine example of a case where the 17hmr would be perfect. I've shot a bunch of foxes over the past 30 years with a 17 rem, and all would have been usable for taxidermy. Conversly, the foxes I've seen shot with the 204 over the past few years would have taken a great deal of work by an experienced taxidermist to be much more than a shoulder mount. That should be read, that you're unlikely to find a steady stream of experienced taxidermists willing to pay $100 for a fox, unless in a bind and needing one in a hurry. While there are beginners in taxidermy, who may be willing to pay prices 2 or 3 times the fur value, most guys who have been at it a few years are pretty tuned into what the fur market is. While there are a few of us that have developed a sideline business of selling completed mounts, in addition to the mainstay of mounting for sportsmen, thats generally a limited market at best.While you might expect a few bucks more than market value for premium quality unskinned specimens, this wouldn't include those with large holes blown through them. Your best bet, if you have a taxidermist or two, that you bring work to occassionally, you're much more likely to find a market, than walking in to studios blind. I could relate dozens and dozens of times over my past 15 years with my full time studio that guys would walk in with all manners of shot, trapped or roadkilled game, with $ signs in their eyes, and feeling they'd hit the lottery,lol. Virtually all were surprised and dissappointed when told I wasn't interested.
I don't mean to sound like I'm raining on your parade, just trying to inject a bit of realism into what this "buyer" told you. If there ever were a viable market for $100 foxes in the taxidermy industry, it would be filled up quickly, as every trapper in the country would be catching them in cages and soft-catch traps which provide a much better taxidermy quality specimen. IMO, your much better off skinning and putting up your furs for the fur market, unless it's something really special and unique. The demand for fox in the fur trade, while not at the levels of '78-'80 when I was selling reds for $80 and grays about 20 bucks less, is still stronger than it's been in quite some time, and you won't have any trouble getting rid of your hides at a decent price.