Economists joke that, whereas they are taught that any barriers to new firms entering a market are bad, allowing profits to be too high, MBA students are taught that "barriers to entry" are good, and shown ways to raise them.

Economists have no quarrel with businesses making profits. The shareholder-owners who provide the financial capital needed to sustain those firms are entitled to a return on their investment, one that reflects not only the (opportunity) cost of their capital, but also the riskiness of the particular business they're in.

Coles and Woolworths have lower prices than IGA and make more money, so it stands to reason they have lower costs. Credit:Glenn Hunt

Economists call such a return on equity "normal profit". But sometimes the various barriers to new firms entering a market limit competition, allowing the incumbents to make profits in excess of those needed to induce them to stay in the industry.

These are called "super-normal" profits (super as in "above"). Now get this: the other name for super-normal profits is "rents" – economic rents, to be precise.