Below vendor cost on the Auction House.

Another make some guarenteed money post, can be much, can be a little depending on what you are used to, awesome if you just rerolled and need some gold.

Do a fast getall scan with Auctioneer (http://auctioneeraddon.com/)
Open your Auctioneer window and press the >> button

Do a vendor search with Auctioneer
Your next step will be to click on the search tab on the bottom.
Then click on Vendor and click search in the left bottom.

Purchase all
The last step is to purchase all items, if you have Allow bids like I do you won't have the item right away. Auctioneer automaticly chooses to buy out or bid so don't worry about it.

Spam the purchase in the left bottom to bid/buy all. You can use this macro to confirm Auctioneer that you want to buy:

/run if (AucAdvancedBuyPromptYes) then AucAdvancedBuyPromptYes:Click() end