What does AI customer support actually cost?
“Pennies per conversation” is the pitch, but a real support deployment re-sends conversation history every turn, injects retrieved knowledge-base context, and still escalates a fraction of tickets to humans. This calculator models all three so you get a credible cost per ticket and monthly spend, side by side with the human-agent equivalent.
How the cost is built up
Because LLMs are stateless, every turn re-sends the whole conversation so far. For a conversation of n turns where each turn adds roughly the same number of tokens, total input tokens scale with the triangular number of turns:
turns_input = tokens_per_turn × (n × (n + 1) / 2)
ai_cost_per_ticket = (turns_input/1e6 × in_price)
+ (output_tokens/1e6 × out_price)
blended = ai_cost_per_ticket
+ escalation_rate × human_cost_per_ticket
That quadratic growth is why long conversations get expensive fast — and why trimming history or summarising it matters.
Worked example
Imagine a support bot handling 500 tickets a day. A typical conversation runs 5 turns, each adding 300 tokens of new content (including retrieved context). The cumulative input across all turns is:
300 × (5 × 6 / 2) = 300 × 15 = 4,500 input tokens per ticket
At a mid-tier model priced at $1.00 per million input tokens and $3.00 per million output tokens with 150 tokens of output per turn:
input cost = 4,500 / 1,000,000 × $1.00 = $0.0045
output cost = 750 / 1,000,000 × $3.00 = $0.00225
ai cost per ticket ≈ $0.0068
With a 20% escalation rate and a human agent handling time costing $4.50 per ticket:
blended = $0.0068 + 0.20 × $4.50 = $0.0068 + $0.90 ≈ $0.91 per ticket
monthly (500/day × 30 days) = 15,000 tickets × $0.91 ≈ $13,600
Compare that to zero escalation with humans alone: 15,000 × $4.50 = $67,500. This is the model the calculator is running.
What affects the result most
- Conversation length. An 8-turn ticket costs more than twice as much as a 4-turn ticket because of how history compounds.
- Context tokens per turn. Knowledge-base retrieval that injects a 500-token excerpt every turn adds up faster than the actual reply.
- Escalation rate. Even a 30% escalation brings the blended cost close to the human figure on expensive agents.
- Model choice. A 10× price difference between a frontier and a lightweight model dominates every other factor on high-volume queues.
Tips to lower cost per ticket
Cap conversation length by summarising old turns rather than re-sending them verbatim. Route trivial intents — password resets, order status — to a cheap model (GPT-4o mini, Claude Haiku, Gemini Flash) and reserve a frontier model for complex complaints. Compress retrieved context with chunking and re-ranking so only the most relevant passage lands in each turn. A well-tuned retrieval pipeline can cut tokens per turn by 40% with no quality loss. Most of the bill hides in re-sent context, not in the final answer.