This is an updated-for-Cataclysm version of TekNoir's updated-for-Wrath (and somewhat recoded) version of AuctionMoney by Equitoen... in case I'm not the only one who really missed it.
--- Original Description ---
AuctionMoney is a conservative Auction House AddOn which provides easy access to information such as:
The number of successful auctions.
The minimum amount of income you can expect from your active auctions.
The maximum amount of income you can expect from your active auctions.
The guaranteed amount of income you can expect from your active auctions.
All of this information is easily accessed using the existing Auction House dialog in the Auctions tab. Just install the AddOn and visit the Auction House!