How much does an AI chatbot cost to build?
What separates a £5k chatbot from a £150k one — and how to work out which one your use case actually needs.
"How much for a chatbot?" is an unanswerable question, in the same way "how much for a building?" is. The honest answer is that four things drive the number, and once you have decided them the range narrows sharply.
Four questions that set the price
Each yes moves the build up a tier. Answer these before asking for a quote.
- Answers from public content onlyWeeks
- Grounded in your internal documentsA quarter
- Takes actions in your systemsFull product build
- Regulated advice, review workflowsBuild + compliance track
1. Does it need to know your business?
A bot that answers from a public website is a weekend. A bot that answers from your policy documents, your pricing rules and your customer's account state is a retrieval and integration project. The second is where most of the cost lives, and it is also where nearly all of the value lives.
2. Does it only answer, or does it act?
Answering is bounded: the worst case is a wrong answer. Acting — issuing a refund, rescheduling an appointment, updating a record — means every action needs authorisation, an audit trail, and a rollback story. Expect the cost to roughly double when a bot gets write access, and expect that to be money well spent.
3. What happens when it is wrong?
A marketing assistant that occasionally misfires is an annoyance. A bot giving benefits guidance, medical triage or financial advice has a regulatory profile, and that means human review paths, logging, red-teaming and sign-off. Budget for the governance, not just the model.
4. How many places does it live?
Web widget only is one build. Web plus WhatsApp plus in-app plus voice is four sets of constraints, four sets of latency budgets and four conversation designs sharing one brain. Channels multiply effort faster than people expect.
Rough shapes
Rather than quote numbers that will age badly, here are the shapes we see:
- FAQ assistant over public content, one channel, no integrations — weeks, not months
- Grounded support assistant over internal documents with handoff to a human — a small team for a quarter
- Acting assistant with authenticated access to systems of record, audit and approvals — a full product build
- Regulated advisory assistant with review workflows and formal evaluation — a full product build plus a compliance workstream
How to test a vendor's chatbot claim
- 1
Bring your own messages
Fifty real, unedited customer messages — not the vendor's demo script.
- 2
Watch the tail, not the head
The common questions always work. Ask about the awkward ones.
- 3
Ask to see the failures
A vendor who can show you what it gets wrong has measured it.
- 4
Check the handoff
What happens when it can't answer decides most of the user experience.
The cheapest mistake to avoid
Do not buy a demo. A chatbot that impresses in a scripted walkthrough tells you nothing about how it behaves on the messy tail of real questions. Ask any vendor to run their system against fifty of your real, unedited customer messages, and to show you the failures as well as the wins.