Consider, for a moment, the qualities of bread.
Bread nourishes us—it's called the “staff of life.” So it makes sense that both bread and dough are slang for money, and that those who support their households are called breadwinners.
In Michael Pollan's deliciously fascinating new book, Cooked, I learned that white flour holds an ancient prestige, as the rich demanded the whitest possible bread and the poor were left to eat the brown bread of the coarse, whole-grain flour. Pollan writes, "Going back to ancient Rome, the shade of the bread you could afford precisely indicated your social standing. To know one's place, Juvenal wrote, ‘is to know the color of one's bread.’"
Gratefully, the color of our bread no longer signals our socioeconomic standing so definitively (and our knowledge of nutrition has toppled the ancient order). But we are constantly exposed to lots of other indicators—which ones do you judge others by, and which do you judge yourself by: Cars, housing, jewelry? Jobs or professions? Vacations?