Imo shadowfang is worth 75k-100keach, 75k being normal price, 100k being desperate. And thats assuming the person that is selling it is paying for the xfer.
Anything over 75k per sf is a good deal imo, but if it adds up to less its really up to the seller, because theres always peaple buying sf's. Im not an expert tho, but I have seen alot of peaple trying to buy and sell shadowfangs and 75k seems about normal.
And unless I get ridiculously lucky on my server's AH, this is why I will never be playing a 19 rogue haha. Even if I found a deal, I think I'd just sell it and profit.
I had one a while back, went back a forth with a few people on forums about prices for them to xfer to me and what not. Was gonna sell it for about 50k. Then just posted in to trade chat 3 times within about 20 mins. 3rd time posting I finally got a decent offer. Guy paid me 70k gold and gave me 5k worth of volatile air/fire/life/water.
But If you're trying to offer someone to buy one. I'd say anywhere from 50-70k is reasonable.