I'd like to add, that undercutting can also be a valuable tool.

Many, many times I see things up for ridiculous prices and I think to myself "there's no way I'd put that much value in this item".

For example, one day I was out making some progress towards Loremaster and I had built up a few stacks of Iron Ore. I checked Iron Ore, not really any in the AH, and I couldn't really get a good idea of the market/price for it, and I knew that JCs don't really prospect Iron Ore, and Engineers/Blacksmiths need it as Bars, not Ore.

So, I check the Bars, and see that people are selling it for 40g+ per stack of Iron Bars.

There's no stinkin' way Iron Bars are worth 40g... I wouldn't pay that if I were the buyer, nor do I feel it needs to be worth 40g; I got several stacks in just an hour or two.

So, I put them up for 25g.

They all sold within 10 minutes.

I don't really care if the guy re-listed, or used it to level his craft; I got my money either way.

People might complain at you for "crashing their market", but I take a small amount of pride for providing more fairly-priced goods to people who need them. Heck, even 25g is a bit steep IMO, but much better than the 40g the other people were charging for it.

Also, when buying, mouse over the Price Per Unit of the partial stacks, people will sometimes throw up partial stacks for cheap just to get rid of it, and make a little money.

For example, I was leveling a tailor and needed silk; I was only short a few stacks until I could do mageweave items. I looked it up on the AH, and I saw stacks of silk going for 1g per. I don't mind parting with 5g or so, to get past that, but then I checked the partial stacks -- 1g per stack of 20 is 5s BO per unit, right? Well, I saw someone had a stack of 8 up for 32s, and someone else had a stack of 12 up for 54s. That's 4.5s BO per unit.

Of course, that's only a few silver in savings, but the same concept can apply for more expensive items, too.

Also, if you want something and don't like the prices, mosey on over to WoWhead and see where the item comes from, and see whether or not you are capable or willing to spend the time to get the item yourself. Sometimes, the price just doesn't merit the time spent. People say "Time is money", but sometimes there are other things you can do at the same time.

For example, say you need a bunch of Runecloth. They want 20g per stack in the AH (This is quite common from what I've seen), and you have a Level 80 character.

Instead of plunking down 20g per stack, try flying yourself over to Blackrock Mountain and making a quick trip through LBRS. You will gain 10-12 stacks of Runecloth (that's 200-240g value) and get 100-120g in chump change drops, and junk items you can vendor. You can also get the achievement for killing Wyrmthalak if you didn't already have it, too! And it would only take you an hour or so to do this.

So, instead of plunking down 200g+ at the AH, you could actually go through LBRS in an hour-hour and a half, and make yourself nearly 400g (Value of the Cloth + coin actually earned) and an achievement.