Most store owners know the selling price and the supplier price, subtract one from the other, and call the difference profit. A year later the store is busy and still not making money. The usual cause is not pricing. It is that they counted part of the cost and treated it as the whole.
Cost per order = total costs for a period divided by the number of orders in that period. Costs split into two groups: variable costs that rise with every order, and fixed costs you pay whether an order arrives or not.
Add them up, divide by orders, and you get one number you can compare against the selling price. That number decides whether your last discount made money or lost it.
The items that change the answer are usually the ones missing from a standard dashboard:
You do not need accounting precision. You need a reasonable estimate, because the decision depends on the gap between 8.50 and 8.86, not on the fifth decimal place.
A store sells an item at 12.000 KD and takes 300 orders a month:
Total: 8.855 KD per order. Margin before any discount is 3.145 KD, roughly 26% of the selling price. That means a 30% discount sells at a loss, even though the number looks attractive on the product page.
First, recalculate monthly, because ad cost moves. Second, split it by channel: an order from a paid ad and an order from an existing follower do not cost the same. Third, check the effect before you cut prices or launch free shipping, not after.
At Q8DM we design and build online stores, and the gap between a store that knows its numbers and one that guesses shows up fast in monthly decisions. Start with one sheet containing these lines and update it every month. If you want Q8DM to help build the store or a simple dashboard for these figures, reach us at https://q8dm.com.