Helm’s Deep, the most recent expansion, has been discounted from $40 to $10. Riders of Rohan, Rise of Isengard, and Mines of Moria are all down to $5 apiece, while you can pick up Siege of Mirkwood for $2.50. Probably the best deal, however, is to pick up the expansion quad pack (all expansions save Helm’s Deep) for $10. So for $20 total, you can snap up every expansion in the game to date and get ready for next year’s trip to Mordor.
Don’t forget that even Saruman was on the lookout for a good deal: “Isengard bids five.”