This is a small auction-house scam:
1. Use your mana or wizard oil until you have only one of the whole stack left.
2. Then put the one which is left into the AH. The price should be lesser then for a whole stack, but still good for you.
People will not recognize that, and pay for a stack, but get only 1 oil.
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Ja, mein Englisch ist nicht das Beste.
mfg