Going back to Accounting 1A in the early 1980s ... large chain grocery stores operate using a different business model. Every year they "invest" $###M in their inventory. They make 1-2% on each sale on average, but they turn over that inventory enough times in a year that the profit from their "investment" is decent. But their net profit from their revenue is still 1-2% Needless to say, Mom-and-Pops cannot use this business model.
Ralph could probably explain the above more clearly. When I took Accounting 1A, B, and C at the local JC, Lotus 1-2-3 was still in the future and VisiCalc was just coming into use for serious accounting. A spreadsheet was still usually a large sheet of paper with lots of eraser smudges.