Once you get past the price of the flights. Everything else is soooo much cheaper in South Korea than almost anywhere I've been.
Every city has cheap motels - they are very clean, all rooms have a toilet, shower, mattress on the floor, and water cooler. You get your sheets and comforter at the desk when you check in - so you know it's clean.
The last time I was there, they were around $30 per night. (Google show that's still about right)
Two of us could typically go out to eat for a total of $10 for two meals and a bottle of soju.
The train system was awesome to get from city to city.
As you can tell, I'll likely be going back. ;-).
I could tell, your enthusiasm for the place was shining through!! No wonder, that all sounds awesome. You don't get prices like that in general in many places!!!