Just saw your question and I wish I could give you a straight answer. The AFCK has been around a long time so finding one, or an original model LNIB my be difficult indeed. Good condition may be more realistic as far as one of the original ones and then I don't know what the value or fair asking price would be. I've seen some on the bay LNIB or close to it where the asking price was so obnoxiously high I wouldn't pay that much even if I had the money on principle. But thats just me. Then every so often I see one pop up here on the exchange or even more so on Benchmades forum at reasonable prices so you just have to keep an eye open and sooner or later you may find a good deal.
Benchmade has released various versions of the AFCK over the years with different or updated steels and the AXIS lock so there quite a few out there. They even released a Gold class or two so the price or value varies greatly. All of them I would say are "Good one's" so as long as it's in good condition I don't see how you can go wrong, as long as you can find one that is.
I have an original model and one of the latest releases with the AXIS lock and M390 steel. They are both great knives and special in their own way, so like I said if you can find one I think whatever version you get you'll be pretty happy with it.
Best of luck!