There R lots of Bitcoin sellers in the world who wanna sell those at Bithumb.
But, 50,000 USD limits under the Korean regulation is the problem.
If you get Significant volume & sell them,
How do you send back USD, EURO, bla bla ..?
You can use any online payment method like Neteller, Skrill, Paypal, Payza, etc. there are a lot of ways to send funds to the US or any other country.