Passage Summary: Economists usually think cheaper prices lead to more sales, which was true for steel; however, when lace became cheap and lost its status as a luxury item, people stopped buying it, proving the rule isn't always right.

Conclusion: The general economic rule that demand increases as prices drop has notable exceptions.

Reasoning: While the rule held true for the steel industry, it failed in the case of the lace market, where lower prices led to a loss of status and a subsequent market collapse.

Analysis: In this 'Role in Argument' question, we need to determine why the author mentions the steel example. The author's main point is that the economists' rule is not universal. By showing a case where the rule *did* work (steel) before showing a case where it *didn't* (lace), the author provides a baseline for the rule's application. This makes the exception even more striking. Therefore, the steel example serves as an illustration of the rule the author eventually intends to qualify or limit.