Alright this a dupe i Found and its pretty old so might not work everywhere
This method is fairly slow and it requires a somewhat laggy server
so here we go
Steps:
1. Aquire the item you wish to dupe, we recommend something with a low auction fee your first few
times because almost nobody gets a successful dupe the first try.
2. Head to Stormwind or where ever your favorite auction house is (any auction house will work).
3. Now steps 4 + 5 must be conducted as QUICKLY AS POSsIBLE!
4. List your auction, prepare everything so you are one click away from being able to list your
item but do not list it yet. (if it is really laggy you may quickly list 3-6 items but be as fast
as possible and immideately proceed to step 5).
5. Click the final button to list your auction and hit alt+F4 to exit the game or unplug your
internet, remember timing is everything here, if you are not fast the AH will have your item and
it will not be copied!
If you timed it right the Auction House will have saved first, and your character will not have
had a chance to save, thus the Auction House will have your item, and it will still be in your
backpack as well. Now either let it sell or cancel it and pick it up from the mailbox
alright and freak out because ALT+F4 is in there its a joke and try to hang a ping over 200 ms
doesnt work on eternion because AH and mailbox dont work (go figure)
Hit me up with comments