here it is use it carefully and u shouldnt get banned, i cant see why u should, but as any other stuff it can get u banned if a gm is in a bad mood.
Code:
Post 8 nexus crystals, or whatever u want to dupe, on the AH
(because its free to withdraw them from the AH and such)
then right as the first auction expired remove all the other auctions by hand from the AH.
The game will send 7 crystals from the auctions expiring and the seven crystals that you have removed from the AH.
Meaning u will get 15 nexus, or whatever, instead of ur original 8.
ENJOY WHILE IT LASTS