WoW:API BuybackItem

Will buyback an item from a merchant if you have the merchant window open.

BuybackItem(slot#);

The slot# = the slot from topleft to bottomright of the Merchant Buyback window.

Aka.

Merchant Buyback Window

Merchant Buyback

 (1)  (2)
 (3)  (4)
 (5)  (6)
 (7)  (8)
 (9) (10)
(11) (12)
                [x Gold,x Silver,x Copper]

[Merchant Tab]  [Buyback Tab]