Worked example: scaling to £20k MRR without a step function

The month-one floor is the easy case. The interesting one is what happens at scale — because the standard objection is that the lean stack only works while you are tiny. The data says otherwise.

Take a founder running at £20,000 monthly recurring revenue. The traditional move is to hire: a marketer to run channels, a half-time SEO contractor, a VA for ops. Call it £6,000 to £8,000 a month in loaded cost the moment those people start, before they have produced anything, and a one-to-three-month ramp before they do. That is a step function landing squarely on your gross margin.

Now run the agentic version. The £105 floor expands as volume forces it — the email tool steps up a tier as the list grows, the CRM moves off free as contact counts climb, you add a paid SEO seat and a sales-intelligence tool. A realistic scaled lean stack at £20k MRR runs £300 to £600 a month all-in. That is roughly 2 to 3 per cent of revenue against tooling, with the founder plus AI agents doing the operating. The cost curve stays close to flat while revenue climbs — which is the entire point of operating leverage, and exactly what the step-function of headcount destroys.

This is not hypothetical thrift. Across the market, SMBs spending $5,000 to $15,000 a month on agencies are reported to be cutting those costs by 60 to 80 per cent by deploying AI agents to execute social, SEO, email, and paid autonomously, and 91 per cent of marketers now actively use AI in their workflows, up from 63 per cent the year before. The lean operator is not the exception any more; the staffed-by-default team is the legacy choice. The mechanics of running the funnel this way are laid out in The Agent-Native Growth Machine.