While experimenting with this I found away to dupe items but the dupe is just a ghost item, it will disappear when relog. If we can find away to keep the ghost item =
Ghost Item dupe:
1) You need at least 2 items in a stack (2 intermediate upgraders for example)
2) put talic + 1 intermediate upgrader in the hero, press the upgrade button, and then keep first-mouse-button clicking the intermediate upgrader which you just put in the hero window.
You will notice that even if you fail or succeed the intermediate upgrader will still be there in a stack of 2.
This is the same for crafters making ammo ect, just keep clicking the item after you pressed the upgrade / create button, and it will go back to inventory.
You can't drop or put the item in the bank, maybe you can put it in the auction though.
If we can find away to exploit this, you could dupe Weapon Upgraders, excelsior pieces / booty ect