Economics student

A decent economics student (or philosopher of economics, at least, lacking deep mathematical tools) looks at objects around him and thinks, "I wonder what the supply and demand for that object is." And when he looks at people he thinks, "I wonder what desires for objects drives their actions." Yet does he ever look deeper than that? Is happiness or sadness; harm or benefit not an object? But people don't respond to happiness, you think, or sadness, or else they would always act smarter, more rational, more harm-avoidant. Or could pain cause benefit for people? Do they desire pain for a reason? One time, years ago, a pathetic female friend of mine said, "People desire pain. It makes them feel distinguished." Somehow I'd thought the same thing, and nodded without saying much. Why could we desire pain?