Skip to the end if you feel this is TLDR;
A tip for would be millionaires out there;
You see a guy trying to control the market, force a specific item to remain a single high price. What do you do? farm that item an post it a silver below his/her price.
This item will be purchased everytime as the seller wants to maintain their monopoly.
Instant sale for maximum profit.
The problem with a monopoly is that you ignore the rules of supply and demand.
You set a price and by purchasing everything under that amount your creating a false demand for that item (atleast under that amount). This in turn will provoke other sellers to fill that demand (thus supply). Now the average ones, which your guide attempts to take advantage of, will just sell at the market price and you will still manage to profit off their items if the items sells at your adjusted price. But the smart ones, those who actually spend time every day doing this, will see what you are up to. They will gather all their stock and post it slightly under your own amount with the intent that *you* purchase the items to fuel your monopoly. The items you buy from them will be filling your with inventory with items you cannot profit from and they will have made top dollar from the transaction.
In a real world situation gaining a reputation with customers is important, consumers have been proven susceptible to advertising. In WoW however you have no way for your name to actually be remembered amongst the population. Advertising is one thing, but customers will just hear the advert an ignore the name. how many people actually pay attention to the seller in an Auction? And once the item has been purchased there remains no way to tell the difference between the item purchased from yourself or one from a different seller. All in all, it is near impossible to create consumer confidence in your work.
The scenario you have posted makes little fesible sense. In the real world a monopoly can control a market; by creating sole purchasing deals with all/most producers of the product, by physically forcing non-compliant groups out of the market, by having an incredibly large store of cash to deal with rogue sale groups. But this is illegal in the real world.
In world of warcraft, your dealing with a world where *anyone* can pick up the trade an be fully skilled in a day, and they will then also begin gathering the unlimited resources. Supply in wow is infinite, but demand (due to there not being infinite players) is not. What you find in a monopoly is that those skilled in the AH will aim to fill your demand until you are out of money and filled with inventory you can only make a loss from. The market itself will be only slightly put out as your reign of the AH will have lasted only a day or two. You will then be in need of more money, and hopefully have learnt your lesson.
Bottom Line:
Monopolies don't work, but please try. I'd love to have your money