I think that in the AH you should be able to sell multiple stacks of an item in one listing So say I had a double chest of iron I wanted to sell, I could put it all up on one listing instead of one stack at a time and for only 10 Could even add an option to buy more than 64 at a time maybe at 128 or around that
You could do this with a chest shop, but I do think this would be useful at decluttering the auction house.
