I've sold a few sheep and goat capes. Price varies a lot based on local demand and cape condition. If a taxi has a buyer lined up, $600 for a shoulder mount seems pretty fair (locally). If they are buying on speculation, expect to get offers that are well under that... $400-$450 were common bids two and three years ago. Bullet holes, excessive blood, or knife cuts on the face can reduce that further. I've found that as the season goes on, sometimes demand can slack as they get all the stock of spare capes they want. Lifesize will get $1000+ and the last one I sold for $1250. Demand is limited, and IME has required marketing and shipping to the L48.
Top dollar requires the cape to have minimal skinning damage around the face and be cut LONG. You will loose money if it's not cut well back on the rib cage.
Ideally, line the buyer up before hand and find out what condition they want the cape. I've gotten pushback for having them turned and salted, but I've also gotten flack for selling them raw and frozen. Different guys want them delivered different ways. It really helps if you have an established relationship and they know what kind of condition you typically can deliver them in.
As a side note, the weight different between a cape and a FS is minimal. About 3 lbs as I recall. Practicality of carrying it out hinges primarily on the bulk.
Yk