i just identified some bow i got cause i was curious (it is a bad bow though so i dont know why only 7-9 dmg) i was wondering what "precious" means cause that is what happened when i identified
from what i can tell... it raises the selling price to npc's a good bit... i've found a few precious, but other than that nothing really special about them.
A 'precious' item simply has it's selling price raised, that's all.
For instance, near Lion's Arch I found a precious Bone Staff. It sold for 9g to start, once indentified it sold for 29g. (I'm not sure is the modifier is always a certain amount or not, I haven't paid any attention.)
Around Old Ascalon, the precious modifier usually bumps items up to 20 gold to sell to the NPC. However, I've found a staff with the precious modifier that sold for 156 gold to the NPC...so I think it might act as a multiplier?