Repeat-purchase economics

Repeat purchasing creates value only when later orders contribute more than they cost to earn and serve. More repeat orders or revenue can look encouraging, but neither shows whether a retention activity paid for itself. Keep three figures separate: contribution from orders already placed, a forecast of future contribution, and the extra contribution an action might cause.

Start with order contribution

For each completed order, begin with sales after discounts and returns. Subtract product cost and costs that vary with the order, such as fulfilment, payment fees and a delivery subsidy. Record which costs are included and use a consistent tax basis. Check shipping charges, refunds and the treatment of recovered stock before comparing periods.

Shopify’s gross-profit-by-product report displays gross profit by product for a selected date range and considers only variants with product cost information recorded at the time of sale. Check the coverage of any report before calling its figure contribution.

Shopify’s product cost field is entered on a product’s page in the admin, under Price > Cost per item. A cost figure that omits shipping or other costs can still be useful for product reporting, but it is not a complete measure of the order’s variable costs. Note the gap rather than assuming the report includes costs that were not entered.

Understand what contribution leaves to cover

Contribution is not the same as net profit. At a business level, total contribution is the pool available to pay fixed expenses and then generate profit, so positive contribution from repeat orders does not alone show that the business has covered its overhead. Keep that distinction clear when presenting results.

Contribution can be expressed in dollars or as a percentage of net revenue. The percentage describes the share left after variable costs; the dollar amount shows the size of the pool available for fixed expenses and profit. Use both when comparing performance, because a stronger percentage does not necessarily mean a larger total contribution.

Contribution analysis can be applied at different levels, including products, product lines, distribution channels and sales by customer. Choose a level that matches the decision, and avoid treating a result for one product or group as if it described the whole business.

Contribution Margin Essentials for Australian E-commerce

Check the cost data behind reported margin

Shopify’s cost-per-item field is the product or variant cost used in its profit reporting. For a resold item, Shopify describes this as the amount paid to the manufacturer, excluding taxes, shipping and other costs; for a product made in-house, the value can be based on labour and material costs. These recorded costs may therefore need to be supplemented when assessing contribution.

In Shopify, profit reports can be found under Analytics > Reports and filtered by the Profit Margin category. The average-profit-margin-by-market report groups metrics such as customer product and shipping charges, duties and import taxes, alongside the corresponding costs paid by the store. It can help reveal market differences, but it does not establish that a retention activity caused them.

Pros and Cons of Using Shopify’s Profit Reports for Contribution Analysis

Keep the customer definition clear

Specify whether “returning” means any earlier store purchase or an earlier purchase in the relevant category. Decide how subscriptions, exchanges and replacement orders count. Incomplete links between online, in-store and guest orders can make a returning buyer appear new.

Report customer and order counts with any returning-customer rate. The rate can rise when new-customer volume falls, even if the number returning stays the same. Compare product groups only over a reasonable opportunity to buy again.

Separate observed value from an action’s effect

Historical contribution describes orders that happened. Customer value forecasts later orders under stated assumptions. Recoverable margin is narrower: the extra contribution a proposed action might produce compared with what would happen without it.

A customer may have bought again without a reminder. Discounting that order could reduce contribution even if the discounted order remains profitable. Code redemption and campaign attribution do not establish an incremental effect. A suitable comparison between customers assigned to an action and customers receiving the usual treatment gives a stronger estimate, subject to uncertainty.

Use contribution as a planning measure

Contribution analysis can inform planning across different sales levels, not just describe completed orders. AccountingTools notes that contribution margin is useful for assessing the earnings available to cover fixed expenses and for planning the contribution generated at varying sales levels. For repeat purchasing, this makes it a useful bridge between observed order economics and a forecast, while leaving the forecast’s assumptions visible.

Use contribution measures as planning inputs, not as evidence that a particular retention action produced additional sales.

Steps to Evaluate Repeat-Purchase Economics

Make a spending decision

Before approving an activity, name the eligible group, action, usual alternative, review period, plausible extra contribution and all costs that the activity changes. Include contact and incentive costs without counting either twice. If evidence for the extra margin is weak, use a bounded provisional budget and review the result before extending it.

Measure contribution per eligible customer, including people who never purchase. Allow enough follow-up to see whether orders were added or merely brought forward, and reconcile discounts, returns and delivery costs. A result from one group and season does not guarantee the same result elsewhere.

Pre-Spending Decision Checklist for Retention Activities