The most common email we get from a UK business owner thinking about an AI agent is some version of: "before we keep talking, roughly what does this cost?" It is a perfectly fair question, and most agencies are weirdly cagey about the answer.
Here is an honest set of numbers based on what real UK SMEs have been paying in the last twelve months. No quotes will be exactly the same, but you will know the territory before you sit down with anyone.
The two parts of the price
Every project has a build cost and an ongoing cost. The build is what gets the agent live. The ongoing cost is the AI usage itself, plus the small amount of human attention to keep it well-behaved.
Both numbers vary, but the ratios are usually more predictable than the totals.
Build cost ranges
For a UK SME, custom AI agent builds typically fall into three brackets in 2026.
Small focused project: £4,000 to £9,000
One job. One channel. Light integration. A web chat customer support agent that talks to one or two systems. A document drafting agent for a single document type. A first sales-response agent tied to your CRM.
Timelines are typically three to five weeks. This is where most first projects sit, and where most businesses should start.
Medium project: £9,000 to £20,000
Multiple integrations, more sophisticated workflow logic, a couple of channels, or a more complex domain. A back-office agent that processes invoices, matches purchase orders and posts to your accounting system. A sales agent that does intake, qualification, follow-up and CRM hygiene.
Six to ten weeks of build is normal here. Pay-back tends to be inside six months when the use case is right.
Larger project: £20,000 and up
Multi-agent setups, deep integrations with custom or legacy systems, voice agents with telephony, anything where the failure cost is high enough that you need a serious testing and rollout plan. Genuinely complex projects can run into the high tens of thousands. Most SMEs do not need this on day one.
Ongoing cost: what to budget
The two ongoing items are the AI usage itself and the maintenance.
- AI usage. For most SME agents, between £50 and £400 a month, depending on traffic and how chatty the agent is. Voice agents and high-volume support agents sit at the upper end. Internal tools used by a few people sit at the lower end.
- Hosting and infrastructure. Often included in the AI usage. Sometimes adds £20 to £100 a month if there is a database or vector store involved.
- Maintenance. A retainer for tuning, adjusting, and adding features over time. Optional but recommended. Usually a few hundred pounds a month for a small project, more for larger ones.
Total monthly running cost for a typical first project lands somewhere between £150 and £500. Compare that to a part-time hire and the maths is usually obvious.
The point is not the lowest possible price. It is the lowest cost of getting it right, including the cost of the times when getting it wrong would have been expensive.
What pushes the price up
Five things drive cost more than anything else.
- Number of integrations. Each system the agent talks to is real engineering work.
- Voice and telephony. Real-time voice is meaningfully harder than chat or email.
- Compliance and data residency. Healthcare, legal, financial services. Doable, but the build is more careful.
- Custom or legacy systems. Modern APIs are quick. A 2007 ERP with a CSV export is not.
- How many edge cases need handling. "Most cases" is fast. "Every case" is much slower and rarely worth it.
What pulls the price down
Three things keep the cost honest.
- Tight scope. One job, one channel, one team. Always.
- Modern off-the-shelf tools. Xero, HubSpot, Shopify, Slack. Easier to integrate, faster to ship.
- A clear definition of done. If you can describe success in two sentences, the build is faster.
Where you should not skimp
A handful of things genuinely matter and are not the place for the cheap option.
- Data safety and the right model provider tier.
- Proper testing before going live.
- A real human-in-the-loop for the first month of operation.
- Logging, so you can actually see what the agent is doing.
What we would suggest
For most SMEs, the right first project is in the £5,000 to £10,000 range. Specific. Useful. Pays back in a quarter or two. Once that is live and working, the case for the next one writes itself.
If you are sizing up a specific build, our two-week strategy audit ends with a written estimate against your real workflow. Or, if you already know what you want, give us the rough shape and we will come back with a real number, not a brochure.