Are you about to sign an agency retainer without being sure it fits where your business actually is? Or are you weighing whether a fractional arrangement makes more sense than an in-house hire?
If you choose the wrong marketing model, you don't just waste budget, you lose months of momentum, stall pipeline growth, and create dependency you can't easily undo. The financial and strategic cost of getting this decision wrong is significant, and most businesses only realise it six to twelve months in.
After working with dozens of B2B businesses to restructure underperforming marketing functions, one thing is clear: the "best" model depends entirely on your stage, structure, and goals, not what worked for someone else.
In this article, you'll find a direct cost comparison, a head-to-head trade-off table, ROI guidance by revenue stage, and a five-step decision framework to help you choose the right model with confidence.
When you choose a marketing model, you're deciding how much control, cost, and capability your business will own, and that decision shapes your marketing trajectory for years, including how dependent you become on external providers.
The three main marketing engagement models are: agency (outsourcing activity to an external firm), in-house (employing full-time marketing staff), and fractional (retaining a senior marketer on a part-time, flexible basis). Each represents a different trade-off between cost, control, speed, and strategic depth.
| Model | What it means | Best described as |
|---|---|---|
| Agency | External firm manages your marketing | Outsourced delivery |
| In-house | Full-time employed marketers | Internal team |
| Fractional | Senior marketer, part-time engagement | Flexible leadership |
The defining difference is ownership: agencies retain the knowledge and systems when you stop paying; in-house teams build internal capability over time; and fractional arrangements can go either way depending on how the engagement is scoped.
In 2025, a full-service agency typically costs £3,000–£15,000+ ($4,000–$20,000+) per month on retainer; an in-house marketing function commonly runs £60,000–£200,000+ ($80,000–$270,000+) per year in salaries; and fractional support ranges from £2,000–£8,000 ($2,700–$10,700) per month.
In-house hires carry employer on-costs of 20–30% above salary, meaning a £70,000 ($93,750) marketing manager hire actually costs £91,000–£100,000 ($121,000–$133,000) once you factor in employer National Insurance, pension contributions, and recruitment fees.
Agencies often add project fees and ad-spend management on top of retainers, and fractional costs vary considerably by seniority, hours committed, and whether execution is included.
| Model | Monthly cost | Annualised | Key hidden costs |
|---|---|---|---|
| Agency | £3k–£15k+ ($4k–$20k+) | £36k–£180k+ ($48k–$240k+) | Project extras, junior staff on accounts |
| In-house | £5k–£16.7k ($6.7k–$22.4k) | £60k–£200k+ ($80k–$270k+) | Employer NI, pension, recruitment |
| Fractional | £2k–£8k ($2.7k–$10.7k) | £24k–£96k ($32k–$128k) | Execution often excluded from scope |
Most mid-market B2B businesses fall toward the middle of these ranges — but the hidden costs column is where the real differences emerge.
A quick note on bias: As a fractional CMO, I naturally see this model perform well in many cases, but it is not the right fit for every business, and this article reflects those trade-offs openly.
Assumptions: UK-based B2B businesses. In-house monthly costs derived from typical marketing manager to head-of-marketing salary ranges; treat as estimates. Verify against Reed.co.uk Salary Guide.
Agencies deliver the broadest skill set and fastest deployment; in-house teams offer the deepest brand immersion and executional control; and fractional marketers provide senior strategic leadership without the full-time overhead.
The ratings below are based on typical UK B2B engagements across businesses between £1m and £20m ($1.3m–$27m) in revenue. Individual results will vary depending on the quality of the provider, clarity of strategy, and level of internal alignment.
| Criteria | Agency | In-house | Fractional |
|---|---|---|---|
| Cost efficiency | Medium | Low | High |
| Speed to deploy | High | Low | High |
| Skill breadth | High | Medium | Medium |
| Strategic depth | Medium | Medium | High |
| Brand immersion | Low | High | Medium |
| Knowledge ownership | Low | High | Medium |
No single model wins across every dimension; the decision turns on which trade-offs matter most at your current stage of growth.
Every marketing model carries meaningful risks, identifying them before you commit is how you avoid the most costly ones.
The right safeguard across all three models is the same: define accountability structures, KPIs, and exit conditions before you sign anything.
There is no single model that universally delivers the best marketing ROI, the strongest return depends on your revenue stage, existing marketing capability, and how effectively the engagement is structured and managed.
| Revenue stage | Best-fit model | Core reason |
|---|---|---|
| Under £1m ($1.3m) | Fractional | Senior thinking without full-time cost |
| £1m–£5m ($1.3m–$6.7m) | Fractional + agency hybrid | Strategy and execution without a full team |
| £5m–£20m ($6.7m–$27m) | In-house + fractional oversight | Volume justifies headcount; senior strategy still adds value |
| £20m+ ($27m+) | In-house | Full internal capability delivers the best long-term return |
Fractional models consistently deliver strong ROI per pound for businesses under £5m ($6.7m); in-house generates the highest long-term ROI once marketing volume and repeatability justify the ongoing headcount.
ROI estimation framework:
(Revenue generated by marketing - Total marketing cost) / Total marketing cost x 100 = ROI %
Include fees, salary on-costs, tools, and ad spend in your total cost figure. If direct revenue attribution is not yet possible, use pipeline value as a working proxy.
Worked example: A business at £2m ($2.7m) revenue invests £3,500 ($4,688) per month in a fractional CMO, £42,000 ($56,250) annually. If that engagement generates £210,000 ($281,250) in tracked pipeline value, the ROI is 400%. The same £42,000 ($56,250) invested in a mid-tier agency retainer might generate equivalent pipeline, but if that pipeline was generated without building internal capability, future ROI depends on continued spend rather than compounding ownership.
To choose the right model, you need to answer these six questions first, because the "best" option on paper is rarely the best option for your specific stage, budget, and capability.
Most growth-stage businesses benefit from a hybrid approach, such as a fractional CMO directing strategy while an agency handles execution, rather than treating the three models as mutually exclusive.
The most common questions buyers ask when comparing these models centre on cost thresholds, timing, and how to measure returns fairly.
Yes, and for most growth-stage businesses, that is the right move. A fractional CMO directing strategy alongside an agency handling execution is a common and effective combination.
A fractional CMO takes ongoing strategic ownership of your marketing function on a part-time basis. A consultant typically delivers a project or recommendation without ongoing accountability for results. See my Fractional CMO service page for more detail.
Track pipeline generated, cost per qualified lead, and revenue influenced, not activity metrics. Set these benchmarks before the engagement starts, not three months in.
B2B businesses at growth stage (£1m–£5m / $1.3m–$6.7m) typically see the strongest results from fractional or hybrid models. Agencies suit project-based or channel-specific needs; in-house makes sense once marketing volume is consistent and repeatable.
When you need fast execution across multiple channels and do not yet have the volume to justify a full-time hire. Agencies offer speed and breadth; in-house builds ownership over time.
A useful tipping point is when your marketing activity is consistent enough to justify a full-time salary and when the volume of work exceeds what a part-time engagement can realistically deliver. For most UK B2B businesses, that threshold tends to emerge around £5m–£8m ($6.7m–$10.7m) in revenue, but capability need, leadership gaps, and execution volume matter as much as revenue alone.
Before reading this, you had a real decision to make, and probably not enough structured information to make it with confidence.
You now have what you need: cost comparisons, trade-off data, ROI benchmarks by stage, and a five-step framework to guide your next move.
The next step is straightforward: make a decision based on your current stage, not what worked for someone else, and not the model that sounds most credible in a pitch. The businesses that get this right build scalable, self-sufficient growth. The ones that don't stay stuck in cycles of dependency, paying for marketing they don't own, and restarting from scratch every time a relationship ends.
If you want to apply this framework to your own business, this is exactly the work I do with B2B companies, helping them move from fragmented, dependent marketing to structured, self-sufficient growth systems.
Related article: Fractional CMO vs marketing consultant: which one does your business actually need?
If you are ready to move from a model built on dependency to one built on ownership, book a call to explore my Fractional CMO and marketing services.
Tom Wardman is a fractional marketing consultant and Growth Independence Architect™ working with founder-led B2B businesses across the UK. He specialises in replacing agency dependency with self-sufficient growth systems, building marketing engines that transfer fully to internal teams. Tom is one of the UK's first five certified coaches in the Endless Customers™ methodology and the author of Build a Trusted Brand.
Pricing disclaimer: All GBP–USD price conversions are rounded estimates and correct at the time of publishing. Exchange rates fluctuate and figures should be treated as indicative only.