On Wednesday, Reliance Steel (NYSE:RS) joined the parade of U.S. steelmakers reporting massive increases in their profit guidance. Reliance advised investors that current expectations of $0.40 to $0.45 per share in its fiscal first quarter earnings greatly undershot the mark. (But we should point out that Reliance itself gave exactly that same range of earnings guidance in mid-February.) Reliance now expects that earnings of $0.75 to $0.85 will be closer to the truth -- an increase of nearly 350% over the first quarter of 2003.

Like fellow steelmakers Steel Technologies (NASDAQ:STTX) and Nucor (NASDAQ:NUE), Reliance is in the middle of a perfect storm of profitability. Its CEO in Wednesday's press release said, "Metal prices have continued to rise and demand has been even better than we previously anticipated." Selling more goods at the same price is good for profitability. And charging more for the same number of goods in a period of stagnant sales growth works in a pinch. But selling more goods and at higher prices -- a seller cannot ask for a better business environment.

Moreover, Reliance is making its money the old fashioned way: without putting the screws to its customers. In a story published earlier this week, I described how Steel Dynamics (NASDAQ:STLD) and Textron (NYSE:TXT) have been accused of breaching their contractual obligations to sell steel to customer General Motors (NYSE:GM) at an agreed price. While those kinds of business shenanigans may boost profits in the short term, they also give customers excellent motivation to look elsewhere for suppliers -- which bodes ill for Steel Dynamics' and Textron's sales growth in years to come.

Reliance, on the other hand, has entered long-term supply contracts with very few of its customers. So when prices on the raw materials that Reliance uses rise, Reliance is free to pass on the additional costs (and perhaps tack on a bit of profit, one might suspect) to its customers.

And that is only fair. Those customers could have passed the risk of higher raw materials prices on to Reliance, in exchange for the security of knowing how much they would pay in the future. They chose not to.

Investors should not count on today's seller's market for steel makers continuing indefinitely. Nothing does. But if you are looking for a reliable investment, a company that treats its customers fairly is a good place to start.

Fool contributor Rich Smith has no interest in any of the companies mentioned in this article.