It also makes a difference as to his travel time frame. Summer is going to be generally higher, also booking on really short notice--unless there are some last-minute specials lucked into. Based on what everybody is seeing for TransPacs to/from anywhere right now, I'd say $1200 would be a decent fare find. It seems that the days of regularly being able to pick up a round-trip flight from north Asia to the Eastern USA for $800-900 are but a memory.
One thing your son might look into is checking with local Korean agents there for travel to someplace with a huge Korean population--like LAX (Los Angeles Intl). If he can find a great priced ICN (Seoul Incheon)-LAX round-trip, then find another good domestic LAX-IAD (or Reagan or BWI), then that could work. You can also try this with New York JFK. Try United, US Airways, American, and Continental websites directly, and also try the multiairline sites kayak, expedia, orbitz. You may have to play around with the sites a bit.
I agree that the Korean forum doesn't seem to be the most visible place for this request. But I don't have any better ideas right now.