Buy low. Sell high. It's a foolproof way to make money. Unfortunately, in the real world, such opportunities are often illusory.
On September 2, 2008, traders could have bought wheat in Toledo OH for $5.49 per bushel. At the same time, futures traders were willing to buy the same kind of wheat in the same location for $7.44. It appears like there was an easy $1.95 per bushel of profit to be made by buying low and selling high.