Thornmail costs 2,700 gold, and it can be sold for 1,890 gold. You can assemble it by purchasing Giant's Belt (900 gold cost; made from Ruby Crystal and a recipe), Bramble Vest (800 gold cost; requires two Cloth Armors and a recipe), as well as a 1,000-gold Thornmail recipe. Although this is an average price for a legendary item, Thornmail is very inefficient.