A basic ROI formula is useful only when the revenue and cost inputs are trustworthy. For SEO, attribution is often incomplete because prospects can discover a web design agency through organic search, leave, return through a branded query or direct visit, and convert later. If reporting credits only the final visit, the channel that created initial discovery can disappear from the story.
Start by defining the conversion events that matter to the firm: qualified contact requests, booked consultations, proposal opportunities, and closed work. Then decide how first-touch, last-touch, and CRM source fields will be used together. The goal is not to force every sale into a single-channel narrative; it is to make the attribution rule consistent enough that month-to-month comparisons are meaningful. For additional measurement context, review the signals used to judge whether an SEO program is working.
Project economics also change how you interpret the data. A retained client worth $3,000-$8,000 per month and a project worth $15,000-$40,000 create a different threshold for acceptable acquisition cost than a low-ticket service. Those values belong in scenario planning only when they reflect your actual commercial model; they should not be treated as promises that organic search will produce a client at those values.
Before comparing SEO with another acquisition channel, document the agency's real sales cycle, average contract or project value, close rate, and attribution limitations. That gives you a defensible denominator for the SEO investment and prevents a rankings report from being mistaken for a revenue report.