I found some useless bug in the WoW API which allows you to make a 0-copper-auction with a normal command ingame.
Normally the GUI of the auction house does not allow a start price of 0 copper. Sadly you can't make an instant-buy price of 0 copper.
How it works:
1.)
Go to the auction house, switch to the tab where you can add an item.
Put the item you want to sell in the slot of the interface.
2.)
Type this command in your chat and press ENTER:
Code:
/script StartAuction(0.1, 0, 720);
If done correctly, the auction should appear - with the start price of 0 copper.
What does the three parameters do?
"0.1" = The price of the auction. World of Warcraft can't handle 0.1 so it creates an auction with 0 copper.
"0" = The instant-buy price of the item. 1 means one copper. You can't use 0.1 here, it will ignore it and creates an auction without instant buy.
"720" = How many minutes the auction is running. Only 720 (2 Hours), 1440 (1 Day) and 2880 (2 Days) are acceptable values.
You can find an exact description of the command here!
Maybe you can do use this for something, have fun!