"If you want an insulating fiber that is warm, try the wool of a musk ox. It is sold in Alaska. Expensive."
I think Qiviut is over hyped and WAY over priced. It gets it's warmness for tending to have a rather fine/small fiber size. It does have some nice properties in that it's fairly strong and durable even when it the fiber is so fine.
But purely on a warmth to weight basis, good quality Angora Rabbit fur is definitely warmer than Qiviut, because it's also often fairly hollow or medullated and very fine/small size, whereas Qiviut is more solid.
Even super fine and very high quality Alpaca fibers will be near as warm as Qiviut, at a fraction of the cost, because of the air bubbles oft trapped in same, which can make up for the slightly thicker/courser fiber size.
Same with high quality silk. High quality, super fine micron silk, is a bit finer than even Qiviut, and has the interesting property of having a tri-lobal shape which traps more air than the more round fibers of Qiviut and most other animal fibers.
None of the above alternatives are particularly cheap or inexpensive, but compared to Qiviut, they are dirt cheap!
For Gary, regarding the trapped air bubbles as a trend in Alpaca fibers, here is a link to an independent lab which measures the micron size of different fibers. They also take pictures of different fibers. Scroll down to see a sample which represents a trend in alpca fiber.
But again, fiber size is extremely important in understanding the overall warmth of knit or woven garments. A super fine Merino fiber will be more insulating than a coarse Alpaca fiber trapped air bubble or no.
However, as much as i like specialty natural fibers, i've begun to think of Polartec PowerDry High efficiency fabric treated with polygiene as perhaps the most efficient and overall practical garment insulators to date. The kind of fabric that Patagonia uses for their Capilene 4 garments. It's fairly durable (especially compared to most specialty natural fibers, especially Angora, Possum down, and thinner, non felted Merino), traps a lot of air, doesn't weigh much, dries super fast, wicks awesomely, and doesn't stink. It does require an outer wind jacket or the like to get the full insulation, but since most of us carry a wind or rain jacket anyways, not a big deal.