Value is set as items as used or damaged. Not calculated on the fly.

src/engine/objects/Item.java

@@ -52,7 +52,7 @@ public class Item extends AbstractWorldObject {
     public Enum.EquipSlotType equipSlot;
     private boolean canDestroy;
     private boolean isRandom = false;
-    private int value;
+    public int value;
     public OwnerType ownerType;
     public int templateID;
     private long dateToUpgrade;
@@ -781,6 +781,8 @@ public class Item extends AbstractWorldObject {
         if (this.chargesRemaining < 0)
             this.chargesRemaining = 0;
         DbManager.ItemQueries.UPDATE_REMAINING_CHARGES(this);
+        this.value = this.value * (this.chargesRemaining / this.template.item_initial_charges);
+        DbManager.ItemQueries.UPDATE_VALUE(this, this.value);
     }
 
     public void zeroItem() {