The price-cut trap: why a 10% discount needs 50% more sales

A 10% price cut sounds like it needs roughly 10% more volume to compensate. That intuition is wrong, and how wrong depends entirely on your margin.

Take a product priced at 100 with a variable cost of 70. Contribution margin is 30. Cut the price to 90 and the margin becomes 20 — a third of the profit per sale is gone. To generate the same total contribution you now need 30 ÷ 20 = 1.5 times the units. A 10% discount requires 50% more sales.

On a fatter 60% margin the same 10% cut only requires 20% more volume. On a thin 15% margin it requires two-thirds more. The thinner your margin, the more violent the arithmetic — which is exactly backwards from how discounting is usually deployed, since thin-margin businesses discount most.

The mirror image is the good news. A 10% price rise on that 30-margin product lifts margin to 40, so you can lose a quarter of your customers and still make the same money. Price increases are the highest-leverage change available to most small businesses, and the least attempted.

Before running a promotion, calculate the break-even volume lift it demands and ask honestly whether the channel can deliver it. If a discount needs 50% more units and your best month ever was 15% above average, the promotion is a planned loss.

Where discounting does work is when it moves fixed costs you are paying anyway — filling empty capacity, clearing inventory with holding costs, or acquiring customers with genuine repeat value. In those cases model the lifetime contribution, not the single transaction.