Well I was a bit lost in translation with the immigration clerk, but to my knowledge, any US citizen applying for SES through GOES must pay $100USD, and depositing KRW into the machine would cause change to be made after the currency exchange. The only way that's possible is if you have a Korean bank account, upon which the difference would be deposited into that account. I don't know...I was confused by the whole process, too, but it's just easier to bring a crisp $100 bill with you to the interview. Then again, I was there on Sunday night and it could have been the B team working. I tried just about every way on the machine to let me use KRW or debit, but the only way possible was with USD. YMMV