I'm sorry that this thread is a little old, but I can help a lot. There is a WoW addon called "tradeskillmaster". I use it to auction all my items. After you configure it with what you want to sell, it will automatically post auctions however u want. I have it set up mostly to do 5 stacks of 20. When I click the "post" button, it scans the AH, and then shows a button which says "post _____(item)____" or something like that. When I click this button, it posts a single stack of the item shown. (you have to click it a lot). It can be setup however you want it. There is a gold threshhold, where it will not post lower than a certain gold amount. You can tell it to ignore lower quantity auctions when posting. (if a noob posts a single item for 1g, and you want to sell a stack for 40g, it will ignore the scan on their auction and will only undercut whatever stack size you say.)
The only downside to it is that you need to know the market a bit, so you can correctly program the fallback price. If nobody else has an auction of an item up, it looks in your settings and tells it to post at a certain amount. if you ignorantly put down 200g a stack when its really worth 400g, it's on you.
And like I said, you don't even need to scan the AH. It will only scan (to know what to post) for items in your inventory that ALSO are in it's settings. It can also auto cancel your auctions. It scans what you have in the AH, checks if you've been undercut, and will show you a button to click to cancel a stack if it has been undercut.
It's my fav addon for no retard auction house posting and canceling! But remember, it will do what you say. If you program it to undercut by 10g... thats on you. If you program a fallback price that is cheaper than the normal price, thats on you.
Oh, last thing. The scan takes a long time if there is a bunch of things you have that you post with it, so i'd advise multiple bank alts, and use the auto-mailer part of the addon to mail ur alts certain items. (I can set it up to mail my herbs to my scribe and all of my ore to my jewelcrafter) And if you do decide to post on different toons, you can whitelist their names, so you won't undercut yourself on accident if you post same items on different accounts.
I can sell hundreds of auctions a day because it knows to only put 5 stacks in at a time. When people search, they always see 5, not 100. During peak hours, tho, you will want to babysit it to post new auctions as your auctions sell, so you always have them for the lowest price
I hope I helped
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. I have my main bot. I mail it to my bank, which has a gbank connected to all the crafters on my main non bot account. I post mats in AH, then put some in the bank to craft into something else. then i can put item in the bank to sell on my bank alt.