Here are some estimates for what you can expect to spend for cost of living in Korea.
$4.50 (average per meal)
2L Bottle of water
$46.00 (Average Monthly Payment)
$1.10 (distance dependent)
$43.00 (Average for KTX from Seoul to Busan)
$24.00 (Average for Mukunghwa from Seoul to Busan)
$28.00 (From Seoul to Busan)