The world's finest cashmere comes from Mongolian goats tended by nomadic herders. To withstand the bitter climate they live in, cashmere goats not only have a fleece of thick long hairs, but also an undercoat of fine down.
Each spring, this down is combed out and unwanted long hairs, grease, dirt and faeces are removed. Each goat makes around three to four ounces of cashmere which is enough for about half a sweater. Compare this to a regular sheep providing enough wool for three to four sweaters, and you can understand why cashmere is such an expensive material.