'We'll make it back on lifetime value' is not a financial plan unless you know which customers return, when they return and how much contribution remains from each additional order. A subscription brand with recorded renewals and a one-time gift business cannot safely borrow the same acquisition economics.
Calculate contribution by customer cohort
Start with a defined cohort of new customers acquired in the same month. Count initial revenue net of discounts, COGS, shipping, transaction fees, returns and acquisition cost. For repeat purchases, count only actual recognized contribution in later periods, with refunds and retention costs. Do not multiply an optimistic repeat rate by a vague 'average lifetime value' and report it as booked profit.
Illustrative cohort model: 100 customers are acquired at $45 CPA each, for $4,500 total media cost. Each first order contributes $32 before ads, producing $3,200. The cohort starts at negative $1,300 contribution after acquisition. By 90 days, 25 distinct customers place one additional order at $30 pre-marketing contribution, adding $750. The cohort remains negative $550. By 180 days, if 25 additional repeat orders occur at the same contribution and without extra attributed retention spend, total net contribution becomes positive $200. Those assumptions are deliberately simplified.
| Cohort milestone | Cumulative pre-ad order contribution | Acquisition cost | Net contribution |
|---|---|---|---|
| First order | $3,200 | $4,500 | -$1,300 |
| By day 90 | $3,950 | $4,500 | -$550 |
| By day 180 | $4,700 | $4,500 | +$200 |
This is a model, not evidence that a typical Shopify store reaches payback by six months.
What makes a payback estimate misleading
Mixing recent cohorts with mature customers, excluding refunds, treating subscriptions as guaranteed future payments, overlooking ongoing email/SMS costs, and defining a 'repeat purchase' as a reorder placed with another large discount can all exaggerate lifetime contribution.
The operating threshold
Set an acceptable payback period based on working capital, inventory cycles and financing costs. A six-month contribution payback may be sensible for one business and financially impossible for another. Customer retention is valuable only when the realized contribution arrives soon enough and exceeds the cash needed to support it.
Klaviyo's large 2025 BFCM attributed-value results illustrate how much revenue engagement channels can be associated with at scale, but they are not proof of any one store's incremental retention contribution 1.
Use the CAC Payback Model: load cohorts with actual order dates and variable costs, separate realized contribution from forecast contribution and show the first period at which acquisition has genuinely paid back. See the calculator below.
From the field
Client case, anonymized
Fine-art photography ecommerce brand, USA, six months
- 2,400
- Orders
- $417
- Average order value
- $105
- Paid CAC, new customer
- 58%
- Gross margin
A fine-art photography brand sold framed prints in the US over six months: 2,400 orders at $417, which is $1,000,800, on $227,455 of paid media for a blended 4.40x ROAS. Of the orders, 2,160 came from new customers, so paid cost per new customer was about $105.
| Per first order | Amount |
|---|---|
| Average order value | $417.00 |
| Gross profit at 58% | $241.86 |
| Paid cost per new customer | about $105 |
| Gross profit left after paid cost | about $137 |
The first order's gross profit covers the paid cost of acquisition about 2.3 times. Repeat orders were 10% of the total, so the payback does not depend on them.
What this does not show. Gross profit here is before shipping, payment fees and returns, which the source does not break out. Contribution per order would be lower, and the repeat share is one six-month figure, not a cohort curve.
Run the numbers for your store
The values below are an example. Replace them with your own. Nothing you type leaves your browser, no sign-up is needed, and taxes are excluded.
Sources
- Klaviyo, 2025 BFCM performance statement klaviyo.com
- Shopify, analytics definitions help.shopify.com
Nenad Vasic
Founder and CEO of Fenix Network Media. His work focuses on the economics behind customer acquisition, conversion, measurement and profitable growth. Calculations in this article are original; third-party figures belong to their publishers and are credited in the sources.
Model payback using realized customer cohorts
Use your own numbers, then bring the result to a conversation if you want a second set of eyes on the plan.
