The question behind unit economics is whether one transaction, taken in isolation, makes or loses money once every variable cost it triggers has been booked against it. That framing collapses revenue and variable cost onto a single repeatable transaction so the operator can decide whether the model works at one before deciding whether to scale it. The two standard cuts are per order and per customer; for a DTC brand the per-order build is canonical, and the per-customer view extends it across the relationship.
The per-order build walks the variable-cost stack.
Contribution Margin per Order
Contribution / Order = AOV − COGS − Payment Processing − Pick-Pack-Ship − Returns Reserve − Discounts
Subtract allocated CAC to get contribution margin per new customer. Worked example: $60 − $20 − $2 − $7 − $3 − $4 = $24 (40%); minus $20 CAC = $4 new-customer line.
Subtract allocated CAC and the line becomes contribution margin per new customer. Concretely, a $60 AOV that absorbs $20 of product, $2 of processing, $7 of fulfillment, $3 of returns reserve, and $4 of discounting leaves $24 of contribution per order, or 40%. Allocate $20 of CAC against the first order and the new-customer line is $4.
The per-customer view extends the same primitive across repeat orders. LTV sums cumulative contribution margin across the relationship; payback period measures how many months of cohort contribution it takes to recover CAC; LTV:CAC reduces both into a single ratio of whether the customer is ever profitable. None of these are new metrics — they are the lifetime aggregation of the per-order line, with retention and repeat-order frequency doing most of the work between the order view and the customer view.
The healthy bands read off each line. Positive contribution margin per order before marketing is the structural floor: without it, every additional order loses money on the way out the door and scaling makes the hole bigger. Payback inside the cash conversion cycle — recovering CAC before the brand has paid its suppliers and processors — is the goal at scale, because growth then funds itself rather than starving working capital. The bands quoted around LTV:CAC and payback (3:1, sub-three-month, and the like) are operator conventions, not laws; the right targets depend on cash position, growth rate, channel mix, and margin profile.
Unit economics earns its place as the diagnostic frame that separates two common DTC misreads: scaling a top-line-positive but contribution-negative business, where revenue growth widens the loss; and cutting marketing during a cash crunch when the real problem sits in COGS or fulfillment per order. The frame reads off the same P&L the operator already has — what changes is knowing which line to read first.