Schematic: Hard Khorium Goggles

Source
Any mob in Sunwell Plateau has a chance to drop this; the drop-rate is estimated around 0.02%. These goggles are even better than Tier 6 headpiece, thus making the schematic sell for very high Auction House prices in its time. In expansions since The Burning Crusade, the price has gone down tremendously but the rarity still makes it valuable even as an outdated gear piece.