One reframe beats every sales tag: stop tracking the percent off and start tracking the fraction you still pay. The store wants your eye on the savings. Your money cares about the price that survives the discount. Once you think in what you keep, the mental math gets short and the tricks stop working.

The move is turning every percent into the fraction you pay. 30% off means you pay 70%, or 0.7. Two back-to-back 10% discounts come to 19% off, not 20%, because 0.9 × 0.9 = 0.81. This compounding runs both ways: the same multiplying that shrinks a stacked discount is what grows savings when interest builds on interest.