Using the wrong yardstick makes a great business look bad and a terrible one look cheap. Each sector below starts from zero: how the business actually makes money, explained with examples, and only then the handful of numbers that decide its story.
PE compares price to profit. But a bank runs on borrowed money by design, holding ₹10 or more of deposits for every ₹1 of its own. That makes profit look big and hides the real risk, which is not profit but whether the loans get repaid. A bank dies from bad loans, not from a low PE. So you read its loan quality, not its PE.
Gross margin suits businesses where the product varies. Cement is the same grey powder whoever makes it, and it is too heavy to ship far, so it is really a local commodity. What decides profit is cost and distance, captured in one number: profit per tonne of cement. Gross margin tells you almost nothing here.