Poverty penalty

The poverty penalty describes the phenomenon that poor people tend to pay more to eat, buy, and borrow than the rich. The term became widely known through a 2005 book by C. K. Prahalad, "The Fortune at the Bottom of the Pyramid".
An earlier exploration of this was a 1960s sociology study published as "The Poor Pay More" which examined the ways in which retail patterns and a lack of consumer options allowed marginal retailers such as door-to-door salesmen, "easy credit" storefronts and the sale of installment credit agreements to extract profits from low-income buyers, with fewer options and less sophisticated consumer habits.