Hire an SDR or deploy an AI lead machine? The answer is not ideological — it is mathematical. This guide breaks down the real ROI of both options over 12 months, with figures your accountant understands.

The real cost of an SDR in 2026

The full cost of a junior SDR (base salary + variable + employer contributions + tools + management + training + amortised recruitment) is £55,000 to £80,000/year.

Breakdown: base salary £28-38k, employer contributions 13.8% NI, variable 20-30%, tools £3,500-7,000/year, amortised recruitment £6,000-12,000, management 20-30% of sales manager time, 3-6 month ramp-up.

An SDR costs £4,500 to £6,700/month fully loaded. And 59% of SDRs leave their role within 18 months (Sales Insights Lab) — resetting the recruitment and ramp-up counter.

The real productivity of an SDR

A senior SDR generates 25 to 45 qualified leads/month. Time breakdown: 35% research/data entry (AI does this in seconds), 25% sequence management (95% automatable), 20% qualification calls, 15% internal meetings, 5% genuinely value-adding work.

60 to 70% of an SDR's time is spent on tasks AI performs better and faster. Your SDR should be a closer, not a data scraper.

The real cost of an AI lead machine

Initial deployment: £2,000 to £6,500 depending on complexity.

Monthly tech stack: Apollo/Clay + LLM + sequences + booking = £400 to £1,200/month.

Over 12 months, total AI machine cost: £7,000 to £22,000 — 3 to 5 times less than an SDR.

ROI comparison over 12 months

Junior SDR (£60k/year): 18 qualified leads/month from M4, 162 leads over 9 productive months, 15% closing rate = 24 deals at £8k = £192k revenue. Gross ROI: +220%.

AI machine (£15k/12 months): 120 leads/month from M2, 15% closing = 216 deals over 11 months at £8k = £1.73M potential revenue. Gross ROI: +11,400%.

The real equation: SDR + AI machine = your commercial is 3 to 5× more productive because they only handle warm, pre-qualified leads with full context prepared by AI.

Common objections answered

'AI doesn't replace the human relationship': the machine qualifies, the human sells. Optimal division of labour, not replacement.

'Prospects will feel it's automated': a message personalised on a real intent signal is more relevant than a generic human message.

'Our cycles are too complex': the more complex the cycle, the more valuable it is to arrive with a warm, contextualised prospect.

'We prefer to keep control': real-time dashboard, adjustable scoring, modifiable sequences. You have more control with the machine than with an SDR.

How to decide for your company

If your ACV > £5,000 and market of 5,000+ companies: AI machine profitable from M1. If you already have salespeople: add the machine to multiply their productivity by 3. If ICP not yet stabilised: agency pilot for 2 months, then switch to the machine.

Golden rule: never hire an SDR for cold prospecting in 2026. Hire closers. Let AI do the prospecting.