Markup and margin are not the same number
Markup is profit divided by cost. Margin is profit divided by the selling price. Because the denominators differ, the same shilling of profit produces two different percentages, and confusing them is the most common pricing error in Kenyan retail.
The practical consequence is that a trader aiming for a 30% margin who applies a 30% markup ends up at roughly 23% margin instead, and wonders where the money went. Price from cost using markup; judge the health of the business using margin.