there are often good bargains out there, but it usually means going door-to-door with a half-dozen or more places. The shops around the base of Bukhansan Entrance at Ui-dong (O2 World area) are always worth looking in at, or here at Jungro-5-ga area as posted by Sonia:
few shops just N of the Choenggyecheon (stream) and W of Dongdaemun Market in Seoul. There's a Millet store run by Kim Dong-jin, one of Kim Yong-ki (of Korean climbing guide 'fame'). The address is Jongro-gu, Jongro 5-ga 332-1. www.alps-ville.com / misodongjin at naver.com 02)2269-6234/017-339-7115 An old friend's brother works at the near by Black Yak store Jongro-gu, Jongro 5-ga 321-25(u)110-125. The folks working there are super friendly. www.blackyak.co.kr jongro at dongjinl.co.krBoth have some employees that speak English and know something about climbing locally. Find these shops, and you've found the climbing section of Dongdaemun Market-- one of the best general areas to find what you need (and then some) at an affordable price. Some shops don't face the main road/stream. Poke around in the allies a bit! Just slightly less choice/pricier is Namdaemun Market, but bargains can be had! Exit the NW exit from Hoehyeon Subway Station and head right. . . the climbing shops face the main street. . . hard to miss!
Good luck finding a bargain!