I see a lot of complaints about "out of control" AH prices and so forth. I've seen claims that "plat farmers" are responsible for the high prices. I've seen various suggestions around capping or otherwise "controlling" the auction house prices in order to "fix it". I've seen people claim that Plat Farmers "bid up" prices in the AH.
Frankly, these suggestions/ideas bewilder me.
First, Plat Farmers aren't responsible for the high price of items on the AH. Buyers are. Because apparently (some) buyers are willing to pay those prices. As long as there are buyers with money to spend, sellers will try to get every penny they can. If the sellers price their items too high, no one buys them, and the seller pays a transaction cost.
Second, if you try to control the auction house to ensure "reasonable" prices (essentially creating price controls), every interesting item will stop being posted on the auction house - and will show up on the forums instead. Case in point - Wounding of Puncturing items. Now, imagine that no more +6 stat items, no more vorpals/disruptors/paralyzers/smiters/etc, no more holy of pure good/silver bows, no more mithral shields or full plate, etc, etc on the AH. Many, many items are simply far more valuable than others of the same minimum level. (Anarchic Burst Handwraps of slowburst vs. vorpal battleaxe of righteousness)
Third, unless the platfamers are responsible for half the items on the AH, they can't reasonably create artificial shortages for very long. Let me give you an example:
Let's assume there are 100 vorpals that drop on every server on a given day. 5 of those are picked up by plat farmers, the other 95 by regular players. Each player decides for themselves what they would like to receive for the vorpal... let's say they want 100k plat on average for their vorpals, and they set up auctions with a 100k buyout.
The platfarmers, however, want the price to be a million. But they can't make the price a million if there are vorpals out there for 100k. So they have to buy up 95 vorpals at a total price of 9.5 million. So now, they put vorpals back on the market at 1 million. Now, will someone buy some of these vorpals? Probably, but not that many people have 1 million plat lying around, and most of those who do probably don't need vorpals. Maybe they sell 10 of them. So they make 500k plat in profit on that first day.
The second day, another 100 vorpals drop. But this time, some of the people who sold one the day before noticed that their 100k buyout went quickly. So some decide to go for a 200k buyout - let's say the average ends up being 150k. So now the plat farmers have to spend ~14.5 million, and they sell 10, for a loss of 4.5 million.
And the third day, other people notice the rapid buyouts at 150k, and go for 200, etc. In essence, the plat farmers can't control the price because they can't control the supply. Unless they pick up more than half the good items every single day, the farmers can't ever make enough in profits to cover their expenses in creating artificial shortages.
In summation - the prices are an elaborate dance between buyers who want to pay as little as possible, and sellers who want to make as much as possible. If the prices are high, it is because buyers are willing to pay those high prices, otherwise the sellers won't be able to sell them, and will have to lower their prices instead. The auction house works fine as it is.