Suggestion:
Many players camp NMs/HNMs on a regular basis and the crystals that these enemies drop are usually tossed. Since NMs and their drops are supposed to be rare, why not make the crystals rare as well.
My suggestion would be for all NMs to drop HQ crystals instead of normal ones. (Example: Tiamat would drop Inferno Crystal instead of Fire Crystal)
It would have a minimal effect on the economy (only taking away slightly from the cost of acquiring Guild Points) and would give the crystal drops more use than just being thrown on the ground.
Thank you for your consideration.