What makes cashmere so expensive?

I've always kind of wondered what made cashmere so much more expensive than wool other than the fact it's softer. Slate has an answer:

Its costly production process and scarcity. Cashmere comes from the soft undercoat of goats bred to produce the wool. It takes more than two goats to make a single two-ply sweater. The fibers of the warming undercoat must be separated from a coarser protective top coat during the spring molting season, a labor-intensive process that typically involves combing and sorting the hair by hand. These factors contribute to the relatively low global production rate of cashmere—approximately 30,000 pounds a year compared to about 3 billion pounds of sheep’s wool.