for other ideas on the glyph market please follow the link to the free Croda's Inscription Gold Guide
Dust of Disappearance is required when any player wants to change one powerful glyph for another powerful glyph (i.e. those glyphs available to players over level 81).
One blackfallow ink creates 3 Dust of Disappearance or can be bought from a vendor for 12gold 50silver (but only sold to a vendor for 45 silver).
Hence, on my server one Dust of Disappearance would cost 5 to 6 gold to craft allowing the scribe to make at least 6 gold (12.5 less the crafting cost) per sale on the Auction House - assuming the vendor price is setting the maximum Auction House price.
On my server, quantities on the Auction House vary up to 250 and the price has creeped up to 8 gold but has held at cost price for a long time.
My strategy here is not to get involved. Whilst almost all players will buy Dust of Disappearance from the Auction House (if only because they do not know where the vendor is!) the competition is fierce and the profits are low (typically 2 to 3 gold a sale). Bear in mind that my minimum profit per glyph is 40 gold less 15 to 18 gold = 22 to 25 gold.
However, for the young Scribe coming up through the ranks it is a nice low income earner.
. . . . . . . as a side note, because a girlfriend has come onto the scene my posts are now going to go to once every two days!