Patch 3.0.8. still hasn't arrived, but we're hearing more and more news about the changes it will bring. And one change is a major review of all the new enchanting recipes that Wrath of the Lich King introduced. As the situation is now, dusts and essences are simply too expensive, and unless you are wearing epic gear, most enchantments would be more expensive than the armor piece itself, which doesn't make sense. So what went wrong?
Enchanting was never the most popular or most profitable profession. So when Blizzard introduced inscription as new profession, a lot of the people who took up that new profession dropped enchanting for it. At least on my server there aren't all that many enchanters left. In 5-man groups more often than not nowadays there is not a single enchanter, so that bind-on-pickup gear nobody needs ends up being vendored instead of disenchanted. At the same time the other crafting professions now make more useful items, so that the auction house isn't full of cheap crafted items that can be disenchanted. Less enchanters also means less quest rewards being turned into enchanting materials. The fewer enchanters there are, the less enchanting materials are being made, and with low supply the prices are high.
Unless a lot of people go back to enchanting, after having found out that inscription is even less profitable, there is a risk of a permanent shortage of enchanting materials. What Blizzard could to change that is to make it possible to disenchant items for other players, for example in the "not for trade" field of the trading window. So every player who gathered a couple of soulbound items could hire an enchanter to disenchant those items for him, for a fee, and receive the materials. Until then we'll see a lot of rare and epic items vendored, and enchantments remaining unaffordable, even after the patch.