I tried booking an open-jaw in August this year for DUB-ZRH-BKK//HKG-ZRH-DUB but the ticket office quoted a fare in the region of €4K. I have bought open-jaws from them before but these were always within the same country ie. flying to TXL and back from HAM was another I did.

In the end Trailfinders, a very well-known and reputable agent in UK and Ireland, were able to sell the itinerary at €2347 for I class including taxes, so it probably depends what country you're in.