Vicuna is the finest and softest wool on earth. It is also the most expensive fiber you can find.
"Current prices for vicuña yarns and fabrics can range from $1,800 to $3,000 per yard. Vicuña fiber can be used for apparel (such as socks, sweaters, accessories, shawls, coats, and suits) and home fashion (such as blankets and throws). A scarf costs around $1500 while a man's coat can cost up to $20,000." - Wikipedia