Discounts and Profit: How Much Extra Volume Makes a Sale Worthwhile?

A discount increases affordability immediately, but the effect on profit depends on unit costs and the extra volume it generates. A 20% price cut can reduce contribution by much more than 20% when variable costs stay unchanged. Evaluate the contribution lost per sale before estimating the benefit of higher demand.

Start with the original economics

Suppose an item sells for $100 and variable cost is $60. Contribution is $40 per unit. At 100 units, total contribution is $4,000 before fixed costs.

A 20% discount reduces price to $80. The same $60 variable cost now leaves $20 contribution. Price fell by 20%, but contribution per unit fell by 50%.

Calculate the volume required

To preserve the original $4,000 contribution at $20 per unit, you need 200 units. That is double the original volume, not merely 20% more. The general comparison is original units × original contribution ÷ discounted contribution.

If the promotion also adds $500 of incremental advertising, the required contribution becomes $4,500. You need 225 discounted units to cover that advertising and preserve the original contribution after the promotion cost.

Separate extra sales from shifted sales

A campaign may bring forward purchases that would otherwise occur next month. It may also discount orders from customers who were already willing to pay full price. Neither effect can be measured from the discount percentage alone.

Compare the promotion with a reasonable no-promotion baseline. Track returns, fulfillment workload and any lower unit purchasing costs. Higher order volume is not evidence of higher profit until the costs and baseline are considered.

Avoid two common percentage mistakes

Successive discounts multiply. A 20% discount followed by 10% off the reduced amount makes a $100 item cost $72, equivalent to a 28% total discount, not 30%.

Recovering the original price also uses a different base. Increasing $80 back to $100 requires a 25% increase. A 20% increase on $80 reaches only $96.

When does the model stop working?

If discounted price equals variable cost, contribution is zero. No finite sales volume preserves a positive original contribution under that assumption. Below variable cost, each additional unit worsens the modeled result.

Use the Discount Calculator to find the sale price, then the Contribution Margin Calculator to compare the economics before launching the offer.

Related reading

Continue with Wholesale Pricing: Set a Price That Works for You and the Retailer for another part of the calculation.