The problem with heirloom items is this: they are all nominally ilvl 1. That meant that enchantments that had ilvl restrictions could not be placed on heirloom items. Blizzard had three options in dealing with this:
- Do nothing. Leave heirloom items and item enhancements as they are. This wasn't a terrible option, as a matter of fact. It would have meant that heirloom items couldn't have used the latest enchantments, because they were all targeted at ilvl 417 or better items. People had to make do with vanilla enchants and enhancements. While these may have been fine for low-level toons, they were not so useful at higher levels.
- Scale the ilvl of heirloom items with character level. So, a level 10 character's heirlooms might be level 10, instead of level 1,and the same heirloom items on a level 80 might be ilvl 200, for instance. This would mean that the character could progress in the same way as every other character, re-enchanting gear as the gear they had breached the various ilvl barriers for enchanting and other enhancements.
- Remove ilvl restrictions on enchantments, and instead scale the effect of the enchantment with character level. This is the solution that Blizzard chose. It has one big advantage for heirloom wearers: once a top-level enchant is applied, it need never be replaced. It just scales with character level, so it is very convenient for such characters. However, the scaling has a limit. For instance a Burning Crusade enchantment, originally designed for a level 70 character, never scales beyond level 70. It is capped at its effect on a level 70 character.
I'm sure that this convenience is the desired outcome for Blizzard. However it has had one or two unintended consequences. It starts with rare enchantments (such as Enchant Weapon - Spellpower, for instance) that were highly desired, as they were the best enchantments you could get for both heirlooms and low-level twinks. This meant that enchanters actively sought those rare enchantments and would pay dearly for them, which in turn drove adventurers to hunt them down in the world (in effect, it encouraged people to play content that they might otherwise not have seen). In particular, PvP players keenly sought out such enchantments.
That was then. Now PvE heirloom wearers just buy the top level enchantment, for convenience. It scales all the way to 90, whereas as noted, mid-level and low-level enchantments stop scaling before then. For PvP players, the calculation is a little more tricky, but their exact level will often lead them to pick the top-level enchantment, as well. The demand for mid-level and low-level enchantments is seriously reduced. Not to put too fine a point on it, sales of such enchantments have fallen off a cliff. As a result those already crafted were (and still are) being sold off much more cheaply than they used to be, and the crafters are not making any more.
This doesn't only apply to rare enchantments, though it is more pronounced with them. It applies to all low-level and mid-level enchantments. Even those who aren't willing to pay top-dollar for the rarest and best enchantments for their level, and would previously have bought a common mid-level enchantment are buying top-level enchantments, which are more easily found at auction and scale all the way to 90. Or they aren't buying enchantments at all. For levelling has become so much easier nowadays that fewer and fewer levellers are bothering to enchant their gear at all.
So the first consequence is that crafters are not crafting these enchantments (much). Nobody wants them. This reinforces the impression that crafting from level 1 to level 599 is a waste of time and money. There are few enchantments left at lower levels that are selling well (though some still survive, for their beauty rather than their utility). And of course, fewer people are hunting for the recipes.
The second major consequence is that with lower demand for lower level enchantments, there is lower demand for lower-level enchanting materials. But the supply hasn't changed much. The result is that the price of such enchanting mats is also in freefall. And it isn't just enchantments that this applies to. It's all permanent enhancements, such as spellthreads, gems, armor kits and so on. Low level characters are earning less from instances because the mats aren't pulling in as much money as before. Of course, that isn't necessarily a bad thing.
I expect this trend to continue, and for Blizzard to extend it to other items. What's to stop potions, elixirs and flasks being treated in the same way? Under the covers, heirloom gear is already being scaled, and its ilvl is also being scaled in a hidden way, so heirloom wearers can queue for dungeons that have ilvl restrictions on them. What's to stop armour being scaled in the same way?