i am pretty sure (not 100% though) that there is a tax on clothes if you are shipping in more than 100USD worth of clothes. the tax is steep, too. 25% i think.
they really like it when the package comes straight from the place you ordered it from. that way all the price information is easily accessible. i'd say if your shipping a lot of clothes to korea and want to skirt around the tax, get someone to mail it to you and have them keep the value on the box below 100 USD.
again, things might have changed so trust my answer at your own risk