yes you are right you can bid for whatever you like...
-BUT on 320 we have only a few "good" layover for wich eveybody bid for, like: Copenhagen-Vienna-Berlin-Barcelona-Dar es salam....so it's very difficult to have it,and I still remain deeply convinced that the bidding system is not well "balanced"!
-Usualy turnaround flight/4 sectors are much more easy to get.
Cpt salary A-320: ALL inclusive ,average: ..13500.. U$/month OR ..10.000..U$/month+company accomodation. I think new joiners so far don't have the choice: they have to take company accomodation.