it depends if you live near the venue. To tell you the truth I have never seen a concert where they were not selling tickets in front of the venue shortly before the concert. When I was young and did not want to pay the full price I always waited outside the venue until the prices dropped. You just have to be patient. Wait as long as you can, the prices are usually the lowest once the support act has already started with the show. People you bought a ticket but don't want to go just want to get rid of them. This has always worked for me so far
Good luck!
there also seem to sell tickets here
http://www.worldticketshop.de/lander/schweiz (note: I just googled NAS Konzert Schweiz and that was the first link provided. I have never used that service before but maybe it's worth a try as well).