I need to get a flight Prague(PRG) -> Paris(CDG) and Paris(CDG) -> Budapest(BUD), in June. The Air France web system offers me an unbelievable price EUR 680.
If I try similar thing on the Czech Airlines system with a flight PRG->CDG and Geneve(GVA)->PRG, the price is cca EUR 160, similar to a return ticket PRG->CDG.
It seems that Czech Airlines are willing to consider such a ticket as "return" and offer the cheapest tariffs. However, Czech Airlines obviously won't offer me the flight I need.
Is there a way to convince Air France (or someone else) to offer me such a ticket? I know I can use the low-costs, but they are the last option for me, almost equivalent to taking the circa-20-hour trains.
(I apology if any of the "cheap flights" questions treat precisely the "different return" tickets, I wasn't able to find such information.)