I guess most of you already use this, but thought I'd mention it anyway. The complete Auctioneer pack includes the following, briefly explained:

- Provides an option to scan the AH for all items currently for sale. After the scan, every item you hover your mouse over or click on anywhere in the game will be lilsted whith how many times it has been seen on AH, the average price, recommended BO price etc.

- Enchantrix: This module is an addon which predicts disenchant results based off accumulated disenchant data. It does come with it's own database, so right out of the box, it's pretty good at estimating the actual probability of disenchant results.

- Informant: This module contains item information such as which items are parts of quests, vendor buyable and what the vendor prices of items are. It contains it's own database of items so even on a fresh install it's useful, and doesn't have to gather prices.

- BottomScanner allows searching and analysis of the auction contents for specific good buys. When it identifies something that is a "good buy" according to the rules you set, it will alert you and give you the choice to buy the item.

There are some other mudules too. Info is in the link posted above.

Anyway I find this addon a 'must-have'.

I have it couple of months but last time i scanned the AH it was 6 months ago and i never relay on Auctioneer suggested price on AH . But it good to know average price on items

Yes prices vary pretty much and it's recommended to do a scan daily, although I rarely have patience for that...

Each scan takes 15-20 mins, at least on my system. But of course the more often you scan, the more reliable the data will be.