Whether it is a monopoly by LX or a duopoly with OA and LX, it only means that fares on this sector are unrealistically high.
Tried booking a seat from ATH to ZRH and return recently . . . and I could for the same price get a return flight to ATH from Asia!
Longer trips on KLM and Alitalia via AMS, FCO or Milan are only slightly cheaper.
Perhaps it is cheaper to book in either ZRH or ATH for a round trip. Can anyone say how much it costs if you do so in either city?