This is kind of true -- plastic surgery, cosmetic dentistry, and cram schools are probably the three most common businesses in the buildings around Gangnam Station. Wander a few blocks in any direction and it's a little less intense. Elsewhere, I saw ads (mostly in Chinese, or Chinese + English) for cosmetic surgery tourism to Seoul, so that's definitely an industry.
It's kind of inevitable, though; wherever the entertainment industry is going to settle in, there's going to be a large population of people trying to break into it, and hangers-on enjoying the scene.
Visiting the Hongdae district on a Friday night was a parallel experience, only instead of people aspiring to be (or look like) the latest pop idols, it was full of indy music scene people, whether that's hip-hop, pop, metal, jazz, and so on.
I liked the food better in Hongdae, for whatever that's worth. It also had better music shops, even if the clerks in one of them blew me off.
(Edit: Made a few edits to elaborate.)
While Gangnam is known for its expensive, lavish restaurants, the food in Hongdae is indeed more delicious IMO. When have you been to Seoul, by the way? Last year I had a couple American friends from Head-Fi in Seoul where we got together for a humble headphone meet.