Fintech · Payments
Interchange margin varied wildly by acquisition channel.
This marketing & margin audit surfaced $83k in recurring annual margin in a Fintech business, evidenced, senior reviewed, and delivered in 7 days.
The business
A payments company acquired merchants across several different channels at a broadly similar headline customer acquisition cost, and treated those channels as essentially interchangeable as a result. With CAC looking uniform, channel choice was driven mainly by volume and convenience, and the downstream profitability of the merchants each channel delivered was rarely compared.
What triggered the audit
Overall margin varied far more than a stable, uniform CAC could explain, a discrepancy that points to differences hiding beneath the average. The audit split profitability by acquisition channel all the way down to the interchange line, testing whether merchants acquired through different channels actually earned the company the same amount.
What the audit found
Behind the uniform acquisition cost sat wildly different economics. Interchange margin, the core of how a payments business makes money, varied dramatically depending on which channel a merchant came through, because different channels brought structurally different merchant types, transaction profiles and processing mixes. Some channels delivered merchants at a normal CAC but with persistently low interchange margins, meaning they cost the same to acquire but earned far less over their lifetime, while others brought genuinely profitable volume. Because the company evaluated channels only on the similar headline CAC, this margin difference was invisible, and budget flowed indifferently across channels regardless of the profitability of the merchants they produced. The margin left on the table by ignoring this came to roughly $83k a year.
What we changed
Reweighted acquisition toward the channels that deliver merchants with better interchange economics, not merely those that hit an acceptable headline CAC.
Priced or qualified out the structurally low margin segments that certain channels reliably produced, so volume no longer came at the expense of profitability.
Added channel level interchange margin alongside CAC to acquisition reporting, so lifetime profitability is visible at the exact point where budget decisions are made.
Set channel targets on lifetime interchange contribution rather than acquisition cost alone, aligning the team with the profit each channel genuinely brings.
The result
The outcomes were measured for three months after a 90 day implementation period. $83k a year captured by acquiring merchants that actually pay well, not merely cheaply, an annual figure equal to 14× the $5,950 Audit + Sprint fee. For any payments leader, the uniform CAC was the trap: it hid interchange margins that varied wildly by channel. If you judge channels on acquisition cost alone, some may bring volume at structurally worse economics and drag lifetime margin down unseen. Only splitting profitability to the interchange line reveals it. A fixed fee audit does that in days, so budget flows to the merchants that make you money rather than the ones that are simply easy to sign.
From kickoff to signed off findings: 7 days, inside our fixed 5–7 day window.
What the client said
$83k a year found in 7 days
Interchange margin on the worst channel: +0.4% → +2.4%
“Every channel cost the same per merchant, so we treated them as interchangeable. David split profitability down to the interchange line: some channels brought merchants who earned us a fraction. Budget now follows margin, not just CAC.”
David JacksonSenior Auditor · signed this audit off