For a consumer brand that earns its money through repeat purchase rather than novelty acquisition, the leading metric is the repeat-purchase rate. CAC is real, but secondary. A brand with great CAC and poor RPR is acquiring customers it cannot keep — which is a problem the marketing budget cannot solve. A brand with poor CAC and great RPR is a brand that needs to refine its acquisition channels, not its product. The two situations look similar on a P&L until they don’t.
The diagnostic discipline is to look at RPR by acquisition cohort. If the cohort acquired through channel A repeats at 35% in month 12, and the cohort acquired through channel B repeats at 14%, the channels are not interchangeable even if their CAC looks similar. The expensive channel that produces high-RPR customers is structurally cheaper than the cheap channel that produces low-RPR customers, and the brand should consolidate accordingly.
The other useful diagnostic is RPR by product. If the brand has 40 SKUs and 8 of them produce 80% of the repeat purchases, the SKU count is wrong. Either the long tail earns its slot by acquiring new customers who go on to buy the repeat-driving SKUs, or it should be retired. Most brands carry too much SKU complexity and discover it only when they discontinue something and nothing happens.
The hardest thing about leading with RPR is that it takes 12-18 months to measure properly. CAC measures in days; RPR measures in quarters. Brands that are impatient — or whose investors are impatient — will gravitate toward the metric that measures faster, even when the slower metric is the more important one. Building the operating discipline to wait for the RPR data, and to make the SKU and channel decisions on it rather than on CAC alone, is what separates the brand that scales healthily from the brand that scales itself into trouble.
At Useful Buys, the repeat-purchase rate is the leading metric the operating team manages to. Acquisition cost matters; SKU expansion is constrained; the channel mix is allowed to evolve only when the RPR data justifies the change. That discipline is the reason the brand’s unit economics work — and why the operating team is willing to refuse the campaign that would lift sessions but compromise the customer relationship.