Lara GuevaraSupply Chain expert (Product and Service)

Marketing Math Mistake That Destroys Profit

25 Aug 2026 · 1 min

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In this concise commentary, Lara Guevara highlights a common yet costly error in marketing planning: setting promotional discounts based on outdated cost data. She explains that when a product’s landed cost rises but the promo calendar still calls for a fixed discount (e.g., 30% off), the company can end up selling a large portion of the quarter at a loss. Although revenue figures appear healthy because the discount drives sales, the underlying profit is eroded. The core message is that relying on stale cost numbers creates a revenue‑only illusion that masks real profit damage.

This is where I see the most expensive mistakes by a wide margin. Marketing is planning Q4 promo depth off cost numbers somebody pulled in. If your real landed cost moved and the promo calendar still says 30% off on that SKU, you've just planned a quarter of selling at a loss and it will look like a good quarter the whole time it's happening because revenue looks fine. Revenue always looks fine and that's the trap.