The flash-sale maths to do before you lower the price

You have a product that normally sells for £40. A few people have asked whether you will run a discount, and you are wondering if taking 25% off will create enough extra sales to be worth the lower price, the customer questions and the extra admin. Before you publish the code, do the maths that separates a useful promotion from a busy week with less revenue.

Start with the price difference

Write down the normal price and the proposed sale price. If your product is £40 and the discount is 25%, the sale price is £30. You have reduced the price by £10, or 25%.

That £10 is not automatically lost on every order. It is lost on the customers who would have bought at £40 and now pay £30. The promotion has to attract enough additional buyers to compensate for those lower-price orders.

Start with a baseline. If you usually sell 10 copies during a comparable seven-day period, normal revenue is £40 × 10 = £400. If all 10 buyers use the discount, sale revenue is £30 × 10 = £300. You need extra sales to close the £100 gap, before considering fees and your time.

Calculate the break-even sales volume

The useful question is not “How many sales would be nice?” It is “How many extra sales cover the price reduction?” Use contribution rather than headline revenue: sale price minus the costs that rise when you make a sale.

If you expect 10 existing buyers to purchase during the period, the promotion gives up £10 × 10 = £100 of contribution. Each genuinely additional sale contributes £27, so the break-even number of extra sales is £100 ÷ £27 = 3.7. You need four extra sales, not three, because you cannot make 0.7 of an order.

Your break-even target is therefore 14 sales: the 10 you might have made anyway, plus four extra. If you expect the discount to produce only two additional sales, the arithmetic says no. If you expect six, it may work, provided the expectation has a reason behind it.

Include costs that are easy to ignore

For digital products, variable costs may be modest, but they are not always zero. Include payment processing, affiliate commission, paid traffic directly linked to the promotion, refunds you expect to issue and any per-customer delivery cost. Stripe's processing fee still applies when you sell through store.fan, even though store.fan takes 0% of sales. Money goes straight to your own Stripe account.

A discount code can also change the mix of buyers. If you normally sell from your own audience but plan to pay affiliates for promotion, calculate the contribution after commission. You can use [discount codes](/features/discounts) for the offer and review the resulting sales in your storefront analytics rather than treating every order as proof that the campaign worked.

Then add campaign costs that do not sit on an order. If you spend £60 on advertising, and each discounted sale contributes £27, that spend requires £60 ÷ £27 = 2.23 additional sales. Round up to three extra sales before the campaign has recovered the advert cost. Combine that with the earlier four-sale target and you now need seven additional sales.

Price the support burden

A flash sale compresses attention into a short window. Buyers may ask when access starts, whether the code worked, which version they need or whether the offer applies to a bundle. Those messages have a cost even if you do not pay yourself an hourly wage.

1. 1Estimate the number of extra support conversations, such as 15.
2. 2Estimate the minutes required for each, such as 8 minutes.
3. 3Multiply them: 15 × 8 = 120 minutes, or two hours.
4. 4Multiply those hours by the hourly value you use for your work. At £30 an hour, the support burden is £60.
5. 5Add that £60 to any advert or production cost before setting your extra-sales target.

In the earlier example, the campaign now needs to recover £60 of advertising plus £60 of support time. That is £120 ÷ £27 = 4.45, so five additional sales are needed for these costs alone. Add the four extra sales required to offset the lower price for existing buyers, and the campaign needs nine extra sales to break even.

Decide what the promotion is allowed to do

A discount can have a second purpose beyond immediate revenue. You might be introducing a new product, filling places in a live cohort or converting people who have been reading your work but have not bought. State the purpose before you choose the percentage. Otherwise, you may measure the wrong outcome.

• For cash now, measure contribution after fees and campaign costs.
• For a new product, measure paid buyers who complete the first useful action.
• For a course or membership, measure whether the customers remain engaged after the promotion ends.
• For an email list, measure new permission-based subscribers separately from discounted sales.

Keep the offer narrow enough to compare. Choose one product, one discount, one start and end time, and one main audience. A store.fan storefront can support digital downloads, courses and other products in one place; [email marketing](/features/email-marketing) can help you send the offer to a defined audience rather than broadcasting an untracked price change everywhere.

Set a floor and review the result

Set a minimum acceptable contribution before launch. In the example, the discounted order contributes £27 before campaign costs. If that number feels too low after your support time and acquisition cost, change the offer rather than hoping for volume.

You could reduce the discount, offer a bonus that costs little to deliver, limit the number of discounted places or sell a bundle with a higher contribution. A lower percentage is not automatically better, and a bonus is not automatically cheaper: calculate the delivery and support cost of either choice.

After the sale, compare the campaign period with a similar normal period. Record orders, discounted orders, contribution, refunds, support messages and hours spent. If you use [payments](/features/payments) through store.fan, the money flows to your own Stripe account; use your actual payment records and fee statements when checking the result. Your conclusion might be “the sale made money”, “the sale recovered its costs but not my time” or “the sale mainly moved existing buyers to a lower price”. Each answer leads to a different next step.