Undercut auction by a percentage
When changing your default settings, instead of simply undercutting by a set amount (i.e. "1c") you should be able to undercut by a percentage. For example if you are under cutting something that is selling at 100G, and you want to undercut it by 10%, it will post it at 90G. If you are undercutting something that is currently selling for 1g, you will post yours for 90S.