People are probably upgrading jewels and the other fine materials through Jeweller transmutation and the Mystic Forge, respectively. Both methods take quite a bit of dust. Crystalline dust is used in many other recipes as well.
Strangely enough, while most of the t6 mats/lodestones are dropping in price over the past week, I've noticed that the price of dust has nearly doubled. Incandescent dust was selling at 48 coppers each last week and is now at 92 copper. Crystalline Dust was selling around 8 silver each and is now up to 14 silver. I'm not exactly sure what's going on.
Edited by Pariah, 06 February 2013 - 09:07 AM.