I visited Dongdaemun a few times as well, as well as a similar electronics markets in Beijing and Shenzen. Same for clothes.

It does wonders to really make you feel globalization and industrialization at scale in a way that can't be explained or grasped in a classroom, and how much markup gets added before you see the items landing in your local luxury shopping mall, together with nice looking sales people telling you what a bargain you're getting or how special the items are. Don't be fooled.