Current tariff of 4-star airline Etihad Airways allows to book cheap open jaw flights from Europe to South Korea. Air tickets are available from €461 for roundtrip flight including all taxes and fees. As mentioned these are open-jaw flights means that you have to look for multi city connections. In this case you may reach rate for air tickets at this low level when departing from Austria (either Vienna or Salzburg) and returning back to major airports in Germany. (Munich, Dusseldorf, Hamburg, Frankfurt, Stuttgart).
Take this opportunity to visit country which is rich in ancient history as well as leader in hi-tech. Tariff of Etihad Airways allows to book these open jaw flights till the end of June 2014. In case of interest you may book either via Ebookers, Expedia or directly with Etihad Airways.
Booking sample of a flight with departing from Vienna on 14th of May and returning back from Seoul on 28th of May: