Another exploit for Dungeons & Dragons 3rd Edition
 Step by step guide
Level 11 (minimum, will only net 3,000,000) Wizard, with max ranks in Weaponsmithing and the spells Wall of Iron and Fabricate.
1. Cast Wall of Iron, creating a wall 55ft*5ft*2in=45.83cu ft of iron. This step costs 50gp in material components.
2. Cast Fabricate, converting 11 cu ft per cast into masterwork daggers. With 14 ranks in Craft (Weaponsmithing) and a wizard's crazy Int, you can't fail. Repeat until only 1-2 cu ft of iron remains. (4 casts). This consumes your 5th-level slots for the day, and takes 4 and a half minutes.
The density of iron is 491lbs/cu ft. Thus 44 cu ft of iron weighs 21604 lbs. A dagger weighs 1 lb. Thus we create 21604 masterwork daggers, which sell for 151 gp each. That's 3,262,204 gp. Over 3 million gp. At level 11.
 Additional details
Teleportation will solve the economic problems; by selling to the entire world instead of just the local pawnshop, you can easily find a market. And then spend your money to set up lots of local branch offices, with people capable of casting Sending or whatever to keep you informed of how business is going and what local demands are. Use this to track warfare and sell your weapons wherever they are needed. You probably won't be able to sell the maximum output of a level 20 wizard, but you'll make a very, very good profit, not to mention a lot of friends in high places if you sell at a bit below normal price.
20th level wizard, without using any slots above 6th level.
- Volume of Iron = 5*5*20*(5/12)=208.33cu ft.
- Castings of Fabricate = 10 (use 6th level slots to fill as required)
- Fabricate time = 20 minutes per day
- Mass of Iron Fabricated = 200*491=98200 lbs.
- Number of Mwk Daggers = 98200
- Payout = 98200*151=14,828,200 gp
- Profit = 14,827,700 gp. Per day.
Note: If your DM (assuming he wasn't sensible enough to put a stop to this before it begins) happens to fumble upon a Wall Street Magazine article in his basement toilet, he'll recognize the law of supply and demand, which states that while the demand for said mwk daggers are roughly unchanged, the supply just sky-rocketed, making said daggers essentially worthless. Congrats.
Additional Note: A masterwork dagger would have to be made from steel, not just iron, which requires a significant element of heating, carbon inclusions, and forging. The Fabrication spell wouldn't be able to produce the carbon necessary. You would require a Wall of Steel variant to make this work
Additonal Additional Note: Infinite Multiverse == Infinite Demand. Suck on that, Malthus!
That said, you can still crash the iron market at will.
 See also