Marketing agency vs in-house hire: a worked London cost example

Mistake: treating salary as the whole cost

The costliest mistake is treating salary as the full price of an in-house hire. Salary leaves out employer costs and setup, while an agency retainer buys a different mix of skills, capacity and control.

Compare first-year commitments on both sides before choosing, rather than setting one payslip figure beside one invoice.

Use a mid-weight manager as a worked case, not a market average: £45,000 in London or £32,000 in Manchester. The planning estimate puts first-year in-house cost at 1.25 to 1.45 times salary once on-costs are included. Treat that multiplier as an illustrative range, not survey data.

The planning multiplier of 1.25 to 1.45 times £45,000 gives about £56,000 to £65,000. The itemised table below is the fuller build-up and totals £63,850 (about 1.42 times salary), inside that range; use it as the working figure. Add recruitment, a laptop, software, training and payroll administration; the practical setup allowance is £5,000 to £8,000. Those lines can move the real comparison well beyond salary alone.

Mistake: assuming a retainer and a role are interchangeable

A retainer is not a salary with employer costs stripped out. It buys agency capacity within an agreed scope; an employee offers closer control and a continuing place inside the business. Compare the work delivered, management input and flexibility, alongside cash, rather than assuming the arrangements are interchangeable.

On these table assumptions, the agency total is lower. The £54,000 retainer is assumed to be twelve months at £4,500 a month for a stated scope, such as paid search, SEO and content support. All figures here are illustrative planning assumptions, not survey data or quotes, so replace them with your own salary band and written agency proposals. The retainer fee guide can frame the supplier side.

The £1,350 pension line is 3% of the full £45,000 salary. The statutory minimum applies only to qualifying earnings between £6,240 and £50,270, which gives about £1,163, so the table is slightly generous and the London total would fall by roughly £190 on the minimum. The Manchester case below uses qualifying earnings.

Mistake: using London pay as the national baseline

London salaries can be 30 to 50 per cent higher than regional equivalents; treat that as a planning range, not a published index. Compare the relevant local role and scope rather than carrying a London assumption into every budget. This keeps geography from deciding the result by default.

For a £32,000 Manchester salary, the worked case adds about £4,050 in employer National Insurance and £770 in pension, before setup. Adding the setup allowance of £5,000 to £8,000 gives roughly £41,800 to £44,800, so a total near £44,000 sits in the upper part of that range. That estimate leaves out the £4,000 of management time counted in the London table, and no Manchester agency retainer is costed here, so it is not a like-for-like comparison. Get written quotes for the same scope. Check regional salary bands and London assumptions against the role you actually need.

Mistake: buying capacity that demand will not use

A fixed retainer can be poor value when the work falls away, because the monthly fee remains in place.

The comparison changes when only ten hours a month are needed: a part-time hire can flex down while the agency charge stays fixed. Match expected workload and likely peaks to the scope before choosing.

Agency capacity can span paid search, SEO, content and analytics without recruiting separately for each discipline. That breadth can suit launches or seasonal peaks, while permanent employment can fit steady, repeatable work. A clear agency brief and review of team roles help test whether the proposed scope matches actual demand.

Mistake: leaving the work around the role out of the budget

Holiday cover, sick pay, appraisals and career development need planning even when no simple payslip line captures them. Minimum employer pension contributions are 3% of qualifying earnings. Include those responsibilities alongside equipment and recruitment costs instead of treating the salary figure as the whole employment cost.

Training is another continuing line; as a planning allowance, not a survey figure, set aside 5 to 10 per cent of salary each year for courses, tools and conference time. Customer-data duties also matter: the business remains responsible for its own data when using an agency. Check agency data protection and record relevant amounts in the budget template.

Employment contracts, statutory sick pay, working time rules, redundancy, expenses and benefits also carry costs for an employer. Treat them as prompts to verify which items apply to your hire, rather than adding unsupported amounts to the comparison.

Mistake: treating the first-year result as a permanent verdict

Agency fees are operating expenses, while hiring may create a longer commitment that includes notice periods and redundancy risk. Recheck costs against the workload expected over time, since a first-year total cannot settle every future decision.

Run the calculation with consistent assumptions and revisit it if demand or scope changes. Estimate management time instead of treating it as free, then compare three agency quotes against the same work. A proposal comparison and a marketing cost guide can help keep scope and cost lines consistent.