This is easily the cheapest way to get Leathercraft from 52 to 60-61 since no one exps on Catoplebas anymore. Leaves and water are practically free and tiger hides are incredibly easy to farm in either Batallia or Beaucedine.
What's more, it's possible to get leathercraft to 100 without really needing these, the only reason they get AH'd in bulk is because it's more profitable then NPCing them and they do sell.
Under these conditions, it's easy to see a large supply popping up from time to time, and large supply with no change in demand is invariably a price drop.