Returns the item level increment recieved when upgrading. The item level increment returned depends on the type of item, i.e. blue items recieve 8 levels per upgrade while epic items recieve 4 per upgrade (which costs half as much).
This function can currently only be called when at the upgrade merchant.
See also Item Upgrade functions.
levelIncrement- The amount of item levels that are added to an item's current level once upgraded (