I play multiple shards. I will say this. Many of the same names are at spawns on multiple shards. I imagine that on several of these shards the people do not really play them and probably have a less active means of releasing inventory.
This is problematic for them as they do not have other goods to totally justify vendor expenses and do not want to spend more time than they already do on selling the stools. If they try to release the stools for cheaper there, and thus get better cash flow, they devalue their stools on the major shards.
They're almost forced into hoarding the stools to maintain the value of those they have for sale.