My guild recently looted [Ikfirus's Sack of Wonder] and what a wonderous sack it was.
We have a policy of allowing toons in the run to take BoE items as an upgrade for their main spec, but failing that sell the items through our guild bank. The guildie discount for BoE items is around the 65 - 70% mark, which means not only does the toon get a bargain, but everyone else in the run (and the guild as a whole) benefits from the coin (we sell discounted potions / flasks / eternal belt buckles / enchants through the guild bank).
On this occasion, we banked the item after no interest for a main spec upgrade (mostly due to the peculiar itemisation, and us not running a Bear in our raids). When I looked at the auctioneer data for the item, I started to get a little excited. 25k gold seemed... like... a LOT. So I set the guild price at 8k, and went to the AH.
First up, I wanted to list it at an obscene price on the off chance that a guildie wanted it at 8k. 29400 gold would net almost 28k, so I started there. Almost immediately, I received an offer in the mail from someone's bank alt, offering 25k gold. Later in the day I was whispered with offers over 10k, and got the resigned, "some people have too much gold" when I told them our current best offer.
After checking with guildies that could use the upgrade (8k was still a little steep), I met up with our buyer in Dalaran. At this point in the game, the most coin I had amassed across all my toons was 25k gold, so seeing that much in the trade window got my heart beating a little faster. Even my personal throughput of gold through the guild bank of around 20k gold just didn't compare to seeing it all in one lump sum.
My curiosity got the best of me, and I enquired as to who would be wearing the chest... and it turns out it was going to a horde bear tank in one of the more progressed horde guilds on the server. Although I've dabbled in neutral AHs and grabbing the odd recipe or two from the horde AH, I couldn't believe that I hadn't thought of monitoring the horde AH for those must have BoE items (and other potential money spinners).
So much to my surprise, we decided to bank the coin to give us a head start in Cataclysm, should the guild changes require any actual gold.