I have hired a lot of SDRs in-house over the last 18 years. The first ten taught me how to do it. The next thirty taught me how to do it badly without realising. The thing nobody tells you when you make the hire is that the salary is the cheapest part.
I want to make the case both ways here. There is a strong, honest argument for hiring SDRs in-house — institutional knowledge, brand voice, full control of the pipeline function. There is also a strong, honest argument against — five costs most CFOs miscalculate that compound across the first year of a programme.
The five costs that get missed
Recruitment. Agency fees of 20-25% of first-year salary if you go that route. If you don't, then your senior team's time on shortlisting, interviewing, reference-checking and onboarding. Either way, plan on 8-10 weeks of cycle time and around 20% of one full salary in cost.
Ramp. Your new SDR sits at full salary for 4-6 months before producing meaningful pipeline. That gap is real money: a £60k loaded SDR sitting on the bench for five months is £25k of paid salary against zero output. Bridge Group's 2024 SDR Metrics report puts ramp at 3-6 months across the industry. If you forget this in the model, you are quietly inflating in-house ROI by 30%+.
Tech and data. One Apollo or Cognism seat alone is £15-30k a year. Add LinkedIn Sales Navigator, a sequencer, a dialler, an email warmup tool, scheduling software, and you are at £20-40k a year per SDR before you have made a call. Most internal cost models forget this entirely.
Manager bandwidth. Done well, an SDR needs about a quarter of a senior sales leader's time — 1:1s, pipeline reviews, call coaching, performance management. If your sales leader is loaded at £150k, that's £37.5k of management cost per SDR per year. Done badly, you save the management cost and pay it back twice in attrition.
Attrition. SDR roles see meaningful turnover — often 25-35% in year one. When it happens, you re-incur the recruitment fee, the ramp gap, the data and tech reset. Most companies budget for one SDR per year and end up with 1.3 SDR-equivalents of cost across that period.
Stack all of this honestly and a £60k base SDR in London costs £130-170k in Year 1, all-in.
What the maths looks like, side-by-side
I built a calculator to model this properly because I kept seeing the same conversation with founders — they would compare a £4k/month agency retainer to a £45k SDR salary and conclude in-house was obviously cheaper. The retainer was the full cost. The salary was about 30% of the actual cost.
Run your own numbers in our In-House vs Outsourced SDR Calculator — it includes the five missing costs above and lets you set your own values for each. Most companies finish that exercise with a different mental model than they started with.
When in-house is genuinely the right call
I do not run an outbound agency to convince everyone to outsource. About 1 in 4 founders we run discovery calls with leave with the recommendation to build in-house. The pattern is consistent. In-house is the right call when:
You have a senior sales leader with real bandwidth to manage and coach. The number-one predictor of in-house SDR success is having someone in the building who has done it before. Without that person, the function drifts.
Your product needs deep technical or domain expertise to sell well. Outsourced SDRs are good at qualified curiosity. They are not good at deep technical demos. If your sales motion needs the SDR to understand your product at depth, you need them on the inside.
Your brand voice is part of the moat and you do not want it filtered through anyone else. Some founders have a strong, distinctive way of talking to their market and the SDR work needs to sound like the founder. Done in-house, this is achievable. Done at agency arm's length, harder.
Your average deal size is large enough that one closed deal pays for the SDR for a year. Above £150k ACV, the maths becomes attractive even with the full hidden costs. Below £30k ACV, agency volume economics tend to win.
When outsourced is the right call
You need pipeline now. Outsourced delivers first meetings in 4-6 weeks. In-house takes 5-7 months including recruit, onboard, and ramp. If your runway or your board pressure does not allow five months of zero pipeline at full SDR salary, the choice is made for you.
You don't have a senior sales leader who has run an SDR team before. Hiring SDRs without an experienced manager is the single most reliable way to set them up to fail. Better to outsource until you have built the in-house leadership.
You want to test a new market or segment before committing to permanent headcount. Outsourcing is a way to validate that the market responds before you put fixed cost on the books.
Your team is small enough that the recruitment, management, and infrastructure tax of building in-house is disproportionate. Below ~10 SDRs, the agency model usually has better unit economics.
The honest summary
Both paths work. Both fail. The choice is rarely the one that gets made on a single-line CFO comparison. The five costs above are what most internal models miss, and the five conditions above are what most decisions skip. Run the maths properly, decide deliberately, and most of the agonising goes away.
If you want a senior pair of eyes on your specific situation — internal or outsourced, no preference — book a 30-minute call. We will tell you honestly which way the maths runs for you, and if it is in-house, we will help you sequence the build.
