Price wise things are pretty cheap here as long as you stick to Korean food and beer. I like to have a nice steak once in a while but as long as you are not doing that everyday you will be fine. We eat in about 5 days out of 6. We get Pizza Hut every Friday which costs 30,000 won (25 Euro) and have a nice meal and drink on most Saturdays costing usually 60~70,000 (50~60 Euro). I never like to stay out late as there is always football to watch on TV and besides Saturday night is full of people and I'm not fond of that so usually we are home by 12.
For the house bills, it's all very cheap. Electricity, heating (which is electric), Internet, apartment management (for the lady who cleans the halls and takes out the trash) and the phone are all very reasonable. I am really suprised how cheap living is here. If you stick to Korean food and Korean products (clothes etc) then you would save a lot of money here! I know some guys who have saved 1,500,000 won a month out of 2 million which is very good. Generally I am saving that much but make more than others.
Also the housing system here is different. If you have some money then you can put the "key" money down on a house, let's say 20 million won (16,600 Euro). The landlord then takes that money and invests it and you don't have to pay any rent. After a year you can take the money back or stay there. Either way you are literally getting a house for free!
It's true that Korea, Japan and some places in the middle east are the highest paying for English teachers. I guess that not many people come here and since there is such a huge demand there has to be an attraction to entice people to teach here. Good pay, free housing, airplane ticket and a month's bonus seems to be enough to draw people here.