Resources · 3 min read
Cost per conversation: the unit that keeps your AI agent honest
The monthly bill says how much you spent; it doesn't say on what. The conversation is the unit that lets you compare — against last month, against the value of a sale, against a person doing the same job.
The monthly hides; the conversation reveals
“We spent this much this month” answers no useful question. Did it go up because there are more customers, or because something broke? Is it worth it against what a sale brings in? Cost per conversation — what a full conversation consumes, from hello to resolved — is the unit that turns those questions into arithmetic. Without it, “is this working for us?” gets answered by feel.
A conversation is not one model call
Every turn queries the model; a serious answer also queries the catalog, validates against rules, and sometimes rewrites. A twenty-turn assisted sale multiplies all of that — which is why the store-hours question costs cents and the sale costs more, and why the average lies: look at the distribution. Well designed, the order of magnitude is cents, not dollars. If it gets close to what a sale brings in, the problem isn't the AI: it's the design.
The silent death: running out of credit
The API runs on credit, and credit runs out. An agent without credit shows no error and offers no apology: it just stops answering — on a Saturday, typically — and customers write into the void while everyone's dashboard stays green. Two minimum guards: an alert before the edge, and auto-reload with a cap. It's plumbing. And it's the difference between a normal weekend and a Monday of complaints.
The number across the table: what a conversation is worth
Cost only means something against value: how many conversations end in a sale, an order taken, a question resolved without touching payroll. If a thousand conversations cost what one hour of one person costs, and they handle what used to take a month, the argument about cents is over. And if they resolve nothing, the low cost doesn't save the system — it just makes the failure cheaper.
Ask for the number
If you already run an agent: cost per conversation for the month, its distribution, and the credit alert — three things a serious panel shows without being asked twice. If you're about to hire: ask who pays for the API, and ask to see a real month's cost per conversation from another client, anonymized. If the number doesn't exist, nobody is watching it — and what nobody watches surprises you at month's end.
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