My all time personal favourite sock for all year hillwalking is the Smartwool Hiking Medium Crew. A blend of 74% merino wool, 25% nylon and 1% elastane, they are the one-time winner of the Backpacker Editor's Choice award. TGO regulars, Chris Townsend and Cameron McNeish have applauded them and I adore them. They breathe well, feel extremely comfortable and keep my feet warm in even the coldest conditions. In winter, I add a Bridgedale Coolmax liner to the mix. Sad thing is, they cost between £12 and £13 each.
However this morning, in Costco, I saw these - Kirkland Signature Outdoor Trail Sock, Merino Wool Blend. 71% merino wool, 21% nylon, 7% polyester and 1% elastane, they are almost identical in manufacture, fit, shape and colour to the Smartwool Hiking Medium Crew. Put the two socks together and the only difference is the Smartwool moniker on the instep. They are identical in terms of cushion and thickness and have the same elastane arch brace the Smartwool sock does. Turn them inside out and the weave is identical as is the colour of the wool. Apart from the addition of polyester, which is unlikely to make them less breathable or dry any slower (my only qualm with the Smartwool sock), the only difference is the price: £8.79 for four. I've yet to wear them in anger, but they are certainly worth testing.
Scratching your chin? I didn't for long...
Update as of 18th December 2010 - I have been wearing the same pair of the Kirkland merino socks now for 5 days solid - walking to and from work (3km each way), during work, in and out of snow (in Innov-8 Terroc 330's) and in the house. Two things to report - they are still supremely comfortable and they do not smell at all. These are a true bargain.