Marketing agency, in-house, or AI — what actually works for a sub-£500k business?
An honest comparison of marketing agencies, in-house hires, and AI-led platforms — with the math on cost, speed, and quality for businesses doing £10k–£500k/month.
If you're running a business doing £10k to £500k a month online, and you've got more marketing to do than you have time to do yourself, there are three real options. Hire an agency. Hire in-house. Use an AI platform.
All three get pitched as the solution. None of them are, universally. But the choice you make has a six-figure cost (or benefit) over three years, and most operators pick based on a sales pitch rather than the math.
Here's the honest version.
What you're actually buying
Before comparing costs, name the thing you're buying. It's not "marketing." It's three distinct things:
- Strategy — what channels, what offers, what audience, what messaging.
- Production — writing the copy, designing the creative, shooting the video, posting the content.
- Operation — running the ads, monitoring the campaigns, adjusting the budgets, reporting the results.
Agencies sell all three together. In-house hires handle one or two. AI platforms are best at production, acceptable at operation, variable at strategy.
The right solution depends on which of these three you actually need the most help with. For a sub-£500k business, the answer is almost always production — you know roughly what you need, you just can't produce it fast or consistently enough yourself.
The three-year math
Let's price each option for a realistic operator running at £20k/month in revenue, wanting to grow to £50k/month.
Agency
Typical retainer for a full-service marketing agency working with a sub-£500k business: £2,500 to £10,000 per month. Let's say £5,000/month for the mid-tier agency that does the work half-decently.
- Year 1: £60,000
- Year 2: £60,000 + ad spend scaling ~£2,000/month extra = £84,000
- Year 3: £60,000 + ad spend ~£4,000/month = £108,000
- Three-year cost: £252,000
What you get: a strategy deck, a team of mid-level specialists who work on 8 other accounts, monthly reports, and 2–6 week turnaround on anything that isn't urgent.
In-house hire
One marketing generalist at £45–65k/year + £15k for tools, plus another £30k/year for a designer or content person once you grow. Assume you start with one person, hire the second in month 12.
- Year 1: £60,000 (one hire + tools)
- Year 2: £95,000 (two people + tools)
- Year 3: £95,000 (same)
- Three-year cost: £250,000
What you get: someone who lives and breathes your business, works exclusively for you, and is on your comms channels. But: a limited skillset (one person can't be brilliant at SEO, ads, design, copy, AND strategy), management overhead, and sickness/holiday/churn risk.
AI-led platform (done right)
A platform like Maestren doing the Win-more-work category (SEO, ads, social, copy, design, brand, strategy, conversion) costs roughly £495/month at the full-platform tier. Add a part-time human for strategy oversight and client relationship work — call it £1,500/month, one day a week.
- Year 1: £23,940 (£5,940 platform + £18,000 part-time strategist)
- Year 2: £23,940
- Year 3: £23,940
- Three-year cost: £71,820
What you get: production at a rate no agency can match, consistency a single in-house hire can't sustain, and you pay only for the strategic judgement you can't automate. You're still responsible for the big calls.
The table
| Dimension | Agency | In-house | AI + part-time |
|---|---|---|---|
| 3-year cost | ~£252k | ~£250k | ~£72k |
| Speed to ship | 2–6 weeks | Days | Hours |
| Your management overhead | Low-medium | High | Low |
| Quality ceiling | High (but dilute) | Medium | High (for production) |
| Strategy quality | Variable | Personal, deep | Needs human oversight |
| Consistency | Variable | High | Very high |
| Churn/sickness risk | Account changes | Critical | Zero |
Where each option wins
Pick the agency if:
- You have zero marketing intuition and need someone to tell you what to do.
- Your industry is specialised enough that a mid-tier generalist wouldn't understand it (regulated finance, healthcare, B2B with 2-year sales cycles).
- You value the senior accountability of having someone's name on the contract.
Pick in-house if:
- Your business has a culture or brand voice so specific that only someone full-time inside it will get it right.
- You enjoy managing people and want a team member, not a contractor.
- Your marketing needs vary radically week-to-week in ways a platform can't anticipate.
Pick AI + part-time if:
- You know roughly what your marketing should be but can't produce it fast enough yourself.
- You want to pay for output, not meetings.
- You're fine being the strategic call-maker while the platform handles the production.
- You want to reinvest the £180k savings over three years into ad spend, new hires, or product development.
The uncomfortable truth
For most sub-£500k businesses, the math favours option three, by a lot. £180k saved over three years on marketing execution, redirected to ad budget or product investment, is often the difference between staying sub-£500k and breaking past £1m.
The reason more operators haven't moved to this model is inertia. Agencies and in-house hires are the known options. AI-led operations is the scary option — until you realise the risk you're avoiding costs you £60k/year, every year.
See how Maestren handles Win more work SEO, ads, content, copy, design, strategy — in one platform →What to actually do
If you're deciding right now, the fastest way to get honest data is:
- Pick one category (say, content marketing or lead response) that's currently underperforming.
- Trial an AI-led platform for 3 months on just that category.
- Compare output volume, consistency, and cost against the agency quote you'd otherwise sign.
- If it works, scale. If it doesn't, you've lost three months, not three years.
You can't lose a three-year contract that way. You can learn whether the math on option three is actually true for your specific business — which is worth more than any comparison article.
Including this one.