I get suits and shirts made frequently in Itaewon at Houston and Hamilton Shirts. I'll go to Houston for suits and a few doors down from there is Hamilton 76 Shirts. If you get off at the Itaewon station, exit 4, you can walk straight and Houston and Hamilton will be on your left about 30 yards from the exit.

Suits are usually around 350,000 to 450,000 won and shirts at Hamilton depend on the fabric but they raised prices sometime earlier this year but they're generally between 35,000 and 50,000 won.

If you have a suit that you really like and the design, my suggestion is you take it there and wear it and they'll come close to it. I like suits with a thinner lapel and so I had them make a thinner lapel. You can also customize the pockets and everything... I think the person's English should be good enough (I did it all in Korean...).

One interesting note at Houston, I saw business cards for a few Congressmen there including Mike Honda from CA.