TSM addon has nice option to track your expired/failed auctions, the module required for this is TSM Auctioning. The output in tooltlip looks like this:
http://prntscr.com/75rxlm . You can get more detailed reports within the addon interface, but this way you can quickly valuate any item at a glance.
There is also
this thread in TSM forums about dealing with Salvage Yard greens which I have found to be very useful.
Another worth checking
article about selling greens was recently posted on invaluable GoldQueen blog.