To combat society's worst enemy & cause for the annual and always problematic gold squish, inflation, I believe we need permanent gold sinks that don't go from person to person. This can all be accomplished by placing a few existent (and not yet existent) items across a few trainers of the game. All amounts in gold equate to the approximate values of coins for said sum.

Enchanting Vendor:
Scroll of Illusion LOW ECONOMY IMPACT | ABSENT IN-GAME IMPACT (cosmetic)
75,000 Gold /Relatively low expected demand but a high price/

Scroll of Purification MEDIUM ECONOMY IMPACT ABSENT IN-GAME IMPACT (cosmetic)
9,000 Gold /Low - Medium expected demand for a semi-reasonable price/

Scroll of Deception HIGH ECONOMY IMPACT ABSENT IN-GAME IMPACT (cosmetic)
15,000 Gold /Very high expected demand & large quantity purchases, usually for full sets of 8-10 items depending on class./

(( The amount of people willing to donate directly for transmogification scrolls is BOUND to be significantly lower that the amount of people who would be willing to invest in-game currencies in it. ))

Honor Quartermaster:
Scroll of Honor HIGH ECONOMY IMPACT Use: Increases user's honor gain from honorable kills and rewards by 30% for half an hour. //this does not include using honor-giving consumables such as wintergrasp / arena point tokens// MEDIUM IN-GAME IMPACT (affects honor gain but for a limited time)
3,000 Gold /Very high expected demand.

Arena Quartermaster:
[ANY] Relentless Weapon's Appearance LOW ECONOMY IMPACT ABSENT IN-GAME IMPACT (cosmetic)
20,000 Gold /Medium and yet server profitable impact. A person is vastly unlikely to purchase an item for 20 coins from the store just to spend 10 more on getting its appearance & that person would be more inclined to seek an alternative to that item. This way, at least gold sinks for some desired appearances that are unobtainable elsewise (because why buy relentless for 20 bucks when you can buy a wrathful for 23).

[ANY] Class Trainer
Scroll of Utility LOW ECONOMY IMPACT Use: Resets the user's talents. Cannot be used within battlegrounds or arenas.
500 Gold / Each /Low price but a fair likelihood of a lot of purchases./ ABSENT IN-GAME IMPACT (plainly a quality of life perk)