It's worth shopping around to see if there is another city pair that can be cheaper. Given you are not flying the return, it does not much matter where it is flying to does it? it could be that LIN/MXP/FCO etc could be cheaper to FRA, PRG etc rather than back to VIE.

Last time I threw away a return my outbound was CPH LHR MIA BOG and it was substantially cheaper for the unflown segment to be JFK HEL rather than back from BOG. Just saying