I'm going to come right out and say it: Don't do this. I recently wrote about ways engineers can make money, mentioning (among other things) selling epic ammo to hunters. The problem with making the best raiding and PvP ammo in the game only available from players is that it forces hunters to either find an engineer with the recipe who is willing to do all the crafting by mail, or buy it off the auction house.
What do I have against the auction house, you ask? Well, overall it's an excellent tool and far superior to the much nastier alternative of being forced to actually use trade chat for, you know, trade. It's not perfect, however. In fact, there's one massive glaring inadequacy that can be found.
The "steal from a hunter" button
The AH has, built in to its base functionality, a button. It's big, red and when pushed, takes a small amount of gold from a distracted hunter and puts it into your bags. It's a rotten, nasty trick that I feel should be a bannable offense. Basically, the icon for a stack of, say, Iceblade Arrows looks close enough to the stack of a 1,000 iceblades that maybe every 100th hunter who searches for their ammo for raid that night will accidentally buy a single arrow being listed for sale by an unscrupulous jerk instead of a stack being listed by an honest engineer.
How it could be fixed
While I'd fully support Blizzard handing out 72-hour economic manipulation bans for this scam, all Blizzard would have to do to fix this is make the default auction interface sort these stacks by unit price instead of stack price. To be honest, that would solve a lot of other problems, too. The overall buying interface is dated and clumsy, and one of the biggest advantages that addon-using auctioneers enjoy is that they have the ability to buy smarter. Making the AH interface give as many of those advantages to the end buyers is a change I'd fully support. An overhaul of the buying interface is as needed as the one they made to the selling interface.
The real problem
The real problem with scams like this is that as soon as people get a taste of AH PvP and, say, make their first 20,000g, they start to get cocky and adversarial. They get a lot more economic power than they started off with, and just like arena teams doing world PvP in leveling zones, like to wield this power. I'm all in favor of economic PvP -- however, only against other AH players. When two auctioneers armed with addons, gold, trade skills and inventory battle, the clients win. That's how it should be. In the real world, you can't simply go around the law and rob people if you can't hack it in the real market. You get caught and punished.
Using cheap tricks to make small amounts of gold off honest buyers is a waste of brainwidth. If you want a real fight, try to push your way into an established and profitable market. It takes more work, but the rewards are better. The time people waste opening mail with returned auctions, small amounts of ill-gotten gold and huge amounts of hate mail could have been much more profitably spent learning another trade skill and using it to start an AH supply business.
What you can do
If you see someone posting single bullets or arrows for the price of a stack, open a ticket. If enough people do this, it will get on Blizzard's radar. Also, if you're feeling a little more proactive, feel free to buy a stack of normal priced arrows and sell singles at the same unit price you bought them for. If you paid 3.85g (like in the above example), listing them for 40 copper will push all the scam auctions off the first page and potentially reduce the number of single arrows at full stack price that get sold.
Be aware that overdoing this is no good, either -- if people have to scan past five pages of singles to get to the real ones, you're only replacing one problem with another one. Also, it's trivial for the scammer to simply buy out your auctions to keep their place in the AH. If they do this, you can keep relisting and forcing them to empty a lot of mailboxes.
Being an auctioneer is like being able to print money (or gold, as it were). Wait, that doesn't make sense ... You can print on gold, but you can't print gold. That would be closer to transmutation? I can transmute titanium, but that's only worth it if the price of saronite is low enough to justify the time spent making it. I need some sort of analogy here. ... Whatever, I'll figure it out later. Making gold? Every time they let Basil write Insider Trader, he will endeavor to teach you the tricks of the trade.