"Cost per customer" is one of those terms that sounds precise but is actually ambiguous. Depending on who is using it, it can mean fully-loaded CAC, channel-level CPA, or even unit-economic cost-to-serve. Worth clarifying before basing a decision on the number.
How Joy Subscriptions handles this
Joy Subscriptions, a build-to-order subscription app for Shopify, does not touch cost per customer directly, and instead makes each acquired customer last longer.
Joy Subscriptions does not run or price acquisition; it converts a purchase into a recurring contract and works to keep that contract alive.
The three things "cost per customer" might mean
- Cost per new customer acquired — synonymous with CAC. Total acquisition spend divided by new customers won.
- Cost per customer converted on a specific channel — synonymous with CPA. Media spend on a channel divided by conversions from that channel.
- Cost to serve one customer — a unit-economic figure that includes fulfillment, support, payment processing, and platform fees per active customer. Different metric entirely.
When you hear "cost per customer," ask which one
Finance teams usually mean version 1 (CAC). Paid-ads teams usually mean version 2 (CPA). Operations and CFOs occasionally mean version 3 (cost-to-serve). The numbers can differ by an order of magnitude.
Cost per customer for subscription businesses
For Shopify subscription brands, the most useful framing is to track all three separately:
- CAC — what you spent to acquire each new subscriber.
- Cost-to-serve per cycle — fulfillment + payment processing + platform fees + support allocation per shipment.
- Cumulative cost per customer — CAC plus cost-to-serve across the customer's expected lifetime. The figure you compare to LTV to find true margin.
A note on platform fees
Subscription platform fees show up in cost-to-serve, not in acquisition cost. Joy Subscriptions charges nothing for the first 6 months or up to $1M in subscription revenue, then 1.5% on subscription orders — meaning early-stage merchants can build subscriber base without platform fees eating cost-to-serve, and growing merchants pay proportional to revenue rather than to subscriber count.