In retail stores and webshops the assortment can be managed based on managing and maintaining margins or by focusing on making more money.
Maintaining margins:
Net Profit = Sales x (Gross Margin % - Operating Expenses %)
versus
Making More Money (Deckungsbeitrag)
Net Profit = Gross Margin $ - Operating Expenses $
A simple QUIZ helps illustrate why the percentage framework is sub-optimal:
Imagine you own a store or webshop that sells thousands of products.
The store has an average Gross Margin of 55% minus Selling, General and Administrative operating expenses of 53% equals a Net Profit 2%.
In the store you are selling two comparable products.
You sell the same Quantity, the same number of units of both.
One is a sustainable product, the customers pay you €4 for selling it and then you pay the factory €2 per unit for supplying it.
The factory charges €1 for the other product. At what selling price would it be as (un)profitable as the sustainable product?
The answer is €3 if you actually want to make money.
The sustainable product gives you a €2 contribution per unit (Stuckdeckungsbeitrag db) (€4 selling price − €2 cost). With the same number of units sold, the other product is equally profitable when it also leaves you €2 after paying the factory:
€1 cost + €2 contribution = €3 selling price.
That €2 is what actually helps cover the store’s SG&A (53% of sales on average) and the thin 2% net profit. Percentage gross margin does not.
- Sustainable item: 50% gross margin, €2 cash contribution.
- Same 50% margin on the €1-cost item would mean a €2 selling price and only €1 contribution — half as useful for covering the same operating costs.
Retail systems and textbook “keep the margin %” logic often spit out €2. That makes the cheaper item look fine on a percentage report while contributing far less in euros. Because volume is identical, absolute contribution (Deckungsbeitrag) is the right comparison.
This is the same point made in retail contribution-margin discussions (and in analyses of why percentage mark-ups inflate the consumer price of higher-cost sustainable goods more than necessary).
Same units × same euros left after product cost = same profitability.