The number most businesses track is wrong
When someone asks "is our marketing working?" the typical answer involves impressions, clicks, or maybe cost per lead. None of those tell you whether marketing is making you money. A campaign can generate leads at R20 each and still lose money if those leads do not close, or if the jobs they produce are too small to cover the cost of acquisition plus overhead.
The number that actually matters is cost per acquired customer, what you spent in total marketing and sales costs to get one paying customer through the door. Everything else is an intermediate metric. Useful for diagnosis, but not the answer to "is this working."
The formula, broken down simply
Cost per acquired customer equals total channel spend divided by the number of paying customers that channel produced. If you spent R3,000 on Google Ads last month and those ads generated 40 leads, and your team closed 10 of those leads into paying jobs, your cost per acquired customer is R300.
Now comes the part that determines whether R300 is good or bad: what is your average revenue per customer? If your average job is R1,500, you spent R300 to earn R1,500. That is a 5:1 return, which is strong by most standards. If your average job is R400, you spent R300 to earn R400, and after labor and materials you are likely underwater. Same cost per customer, completely different conclusion depending on your economics.
Why customer lifetime value changes everything
Most service businesses only look at the first job when calculating ROI, but customers often come back. A plumber who fixes a leak today becomes the first call for every future plumbing issue in that household, and eventually the water heater replacement, the repipe, and the fixture upgrade during the kitchen remodel. A roofer who handles one storm repair often ends up replacing the whole roof a few years later when age finally catches up with it.
Harvard Business Review has published research showing that acquiring a new customer costs five to seven times more than retaining an existing one. When you factor in lifetime value, a customer acquisition cost that looks marginal on the first job can be extremely profitable over two or three years. Track how often customers return and what they spend over time. That repeat revenue changes the math on what you can afford to pay to acquire a customer in the first place.
How to compare channels against each other
Calculate cost per acquired customer separately for each marketing channel. Most businesses are surprised when they lay these numbers side by side. A common pattern: Google Ads produces leads at R50 each with a 30% close rate (cost per customer: R167). Facebook produces leads at R25 each with a 15% close rate (cost per customer: R167). A referral program costs very little in hard rand but a lot in time and relationship maintenance. A shared lead platform sends leads at R30 each but with an 8% close rate (cost per customer: R375).
When you compare at the cost-per-customer level rather than cost-per-lead level, the smart allocation becomes obvious. Pour more budget into the channels that produce customers cheaply. Reduce or eliminate spend on channels that look affordable per lead but are expensive per customer.
The one metric that tells you when to scale
Your marketing is ready to scale when you know two things: your cost per acquired customer on a specific channel, and the revenue that customer generates. If the ratio is 3:1 or better (you earn R3 for every R1 you spend on acquisition), increasing your budget on that channel will likely grow your revenue proportionally, at least until you saturate the audience. Below 3:1, you can still be profitable, but the margins get tighter and there is less room for variance.
The businesses that grow predictably are the ones that treat marketing as a system of measured inputs and outputs, not a guess. They know exactly what a customer costs to acquire, what that customer is worth over time, and which channels deliver the best economics. That clarity makes every spending decision straightforward. You are not wondering whether marketing is working, you have the numbers in front of you, updated monthly, and they tell you where to invest and where to pull back.