I'm trying to post an auction of Cobalt Bar on Lordaeron AH, 1 stack of 20 bars for 19 gold, but the auction comes out as 390 gold (20*19) as if I had set the price for one unit.
Auctions of other items seem to work correctly.
I had similar problems with other types of items, but I didn't make a note, and this is something I confirmed a couple of times.
Stackable items have price per unit(or piece, i don't remember) AND total price for the stack you're putting up. The starting bid price is for the whole stack, not per unit.