I don't know about this deal but you have to watch some of this stuff close. My wife sometimes gets deals that have either good prices or no cost. She wants to take me all the time to places and had one about two weeks ago that she was showing me. It was free tours over a 3 day period but you had to pay plane fare. Well, without plane fare is ok. That is what was they said up front. The only problem was , when you got deeper into it you found the tours were free if you had to have a Philippine passport only. I have seen stuff a lot that she gets which have a special price but a poor foreigner in most instances is either a no go, pays full regular price, or has a nice surcharge added in. They will cater to rich Filipinos with the deal though. As far as South Korea, she just went November last year again. And even though it is not that expensive a country, you can bet that during the Olympics, the costs will be to accommodate the Olympic crowd.
Edit: Of course with a US passport on this, no need to worry about the cost of a visa. And I am sure there are other countries with a passport that will work. But not all.