I traded with a chinese farmer, who sold me 10 Primordial Saronites for 500g/each, when they were hovering around 1000g, a few months back.
In my rush to get them onto the auction house, I set up my QuickAuctions to post them, and off they went to the AH. Since this was a highly competitive market, I wanted to keep up with the constant undercuts. Next thing I know, I'm in a cancel/re-post undercut cycle.
I'm not sure who wised up, but someone posted a single Saronite at 300g, roughly 30% of market price. My addon, proceeded to post at 299g... and he snatched up ALL my Saronites, 200g below what I paid, and 700g below market price.
Thresholds.... are your friend.