AI agents for customer support · Part 3 of 14

Build or buy an AI support agent

Three ways to get one, what each costs at 5,000 resolutions a month, and five questions to ask before you sign.

Aakash William
· 4 min read

The short version

You can switch on the agent your helpdesk sells, buy one from a specialist, or build your own on a model. Bought agents mostly charge about $1 to $2 for each conversation they resolve. Building costs cents per conversation in model fees, plus the team that builds and runs it. Choose by how much you need to decide what the agent may do, not only by price.

Three ways to get one

They differ in who builds it, how fast you start, and how much you decide.

Effort to set up and run less more Control over its actions and rules more less Your helpdesk’s agentA specialist vendorYour own build Zendesk, Intercom Fin, Gorgiassuch as Sienaon a model, with your own tools

Your helpdesk’s agent

Zendesk, Intercom Fin, Gorgias

least effort

A specialist vendor

such as Siena

in between

Your own build

on a model, with your own tools

most control
The further right, the more work. The higher, the more you decide what the agent may do and how it is checked.

Your helpdesk’s agent is the quickest start, because it already lives where your tickets are. A specialist goes deeper on actions and integrations. Your own build lets you choose everything, including the work of keeping it running.

What you pay for

Bought agents mostly charge for each conversation they resolve, so the bill grows with their success. Here is 5,000 a month at each vendor’s published price.

Zendesk AI agentsSienaIntercom FinGorgias AI AgentBuild your own $2.00 per automated resolution$750 a month + $0.90 a ticket$0.99 per outcome$0.90 per interaction, yearly planmodel cost only, our estimate Zendesk AI agents: $10,000 a month ($2.00 per automated resolution, pay as you go) Siena: $5,250 a month ($750 platform fee plus $0.90 per automated ticket) Intercom Fin: $4,950 a month ($0.99 per outcome) Gorgias AI Agent: $4,500 a month ($0.90 per interaction on a yearly plan) Build your own: about $360 a month in model cost (our estimate), plus your team’s time $10,000$5,250$4,950$4,500about $360 $0$2.5K$5K$7.5K$10K

Zendesk AI agents

$2.00 per automated resolution

$10,000

Siena

$750 a month + $0.90 a ticket

$5,250

Intercom Fin

$0.99 per outcome

$4,950

Gorgias AI Agent

$0.90 per interaction, yearly plan

$4,500

Build your own

model cost only, our estimate

about $360
Each vendor’s list price on 19 October 2026, times 5,000 a month. Each counts a resolution its own way, and helpdesk seats or plans come on top. “Build your own” is model cost for 5,000 conversations; your team’s time is not in it.
  • What counts differs. Intercom counts an outcome when the customer confirms, when they don’t ask for more help after Fin answers, or when Fin completes a workflow, hand-overs included. Gorgias counts a request resolved without a person, and if your team replies within 72 hours it is billed as a ticket only.
  • Per action, not per resolution. Salesforce charges $0.10 per Agentforce action, so a conversation costs as many actions as it takes.
  • Our build estimate: about 7 cents a conversation, for four turns that each read about 6,000 tokens and write about 600, on Claude Sonnet 5.5 at $2 per million tokens in and $10 out.

The cost nobody prices: one agent per tool

Each vendor’s agent keeps its own settings. If support and billing each run their own agent, a limit set in one is invisible to the other.

One customerSupport agentBilling agent Refund €40Credit €40 your policy: €50 a yearin the helpdesk, limit €50in billing, limit €50 within its own limitwithin its own limit Together: €80 over your €50 a year asksasks againgivesgives

One customer

Your policy: €50 of goodwill a year.

↓ asks the support agent

Refund €40

Within the support agent’s own €50 limit.

↓ asks the billing agent

Credit €40

Within the billing agent’s own €50 limit.

↓

Together: €80

Over your €50 a year.

Each agent stays within its own limit, and the customer gets more than your policy allows. Only rules both agents check, counted per customer, catch the second one.

Five questions before you sign

1

Which actions can it take, and can you turn each one off?

Start with reading only, then switch on the actions you chose.

2

Can you set limits and approvals per action, outside the prompt?

A rule in the prompt is an instruction, not a check.

3

How does it count a resolution?

It decides your bill. Compare definitions, not only prices.

4

Where is your data processed, and is it used for training?

Get the answer in the contract, not the sales deck.

5

What leaves with you if you leave?

Conversations, knowledge, and the record of what the agent did.

Ask any vendor these five, or ask yourself if you build.

Next in this series

Part 4: writing knowledge an AI agent can use. See all 14 parts.

Where Himmel fits

Himmel is the one set of rules in the third picture: every agent, bought or built, checks the same rules before it acts, counted per customer across all of them.

Sources

  1. Prices and definitions read on each vendor’s own page on 19 October 2026: Zendesk, Siena, Intercom, Gorgias, Salesforce Agentforce.
  2. Model prices: Claude API pricing.