`preferred_local_shipping_charge` is currently in won (this is the 3,000 won for express US shipping). Just talked to Patrick, and we can do this as $3 USD if that's easier. But then I need a convenience method to display preferred_local_shipping_charge in won as well.

Which is easier? Keep this at 3,000 won and convert it before calculating here, or set it to $3 and make a convenience method for looking it up?