Hey, Forrest, I wrote a nice long reply with links and everything, but my computer hung up and I lost it.

Basically a gaiter in that weight of wool is gonna require about 200 yards (possibly up to 300, depending on size), and a pair of gloves will require 200-300 yards depending on style and size. Let's say each will require 250 yards. For a nice superwash merino (not 17.5-micron merino) you can expect to spend $9.50 for 175 yards, which puts you at $28.50 for the whole project, plus one extra skein for safety if you can swing it. For your Darwin yarn, it would be like $34, plus extra for safety.

You can find yarns that probably feel exactly the same as those nice yarns for less, especially if you look at sock yarns, which are usually finer and knit with more stitches per inch. That means more work for your friend, and a lighter fabric, but tighter gauge and smoother feel. Before you spend big money, drop by a yarn store and rub some skeins on your neck Also if you go to a yarn shop, you can return unused skeins for credit or sometimes cash.

Ibex and SmartWool and those guys use REALLY fine yarn, so the fabric is going to be different, but I'm not sure what the end result will be--the yarn is heavier (warmer), but the fabric is more holey (more wind can potentially get through). Your friend could use textured stitches or ribbing to keep more wind out (this requires more yarn for same size), or you could add a fleece panel to the front.

Hope I didn't forget anything and this is helpful! Oh and if you're looking for a pattern, knitters usually call gaiters "cowls," so that might turn up more results. They'll also have more-specific yarn requirements so you won't buy yarn you don't need. Make sure we get to see them when they're done!