Sierra Trading Post has good deals on liner socks if you can find your size etc. These Smartwool liners, while not multipack, are not bad at under $5 a pair with 35% off code (NWM56648, good thru 3/24). http://www.sierratradingpost.com/smartwool-hiking-liner-crew-socks-merino-wool-lightweight-for-men-and-women~p~11903/ . I have a couple pairs and I like them. Mine had no noticeable defects as "2nds".
YCR19213 is a code for at least 75% off but with limited sock options.
ps- first post on BPL!! Feels good to contribute after reading for months :)