Traffic cost is a metric that assigns a dollar value to your organic search traffic by estimating what that same traffic would cost if you bought it through paid advertising. SEO tools like Ahrefs, SEMrush, and Moz calculate this by identifying which keywords your site ranks for, estimating monthly search volume for each, then multiplying by the keyword's average CPC in Google Ads. For example, if you rank #3 for "Ottawa web design" (200 searches/month, $18 CPC) and capture roughly 11% of clicks based on that position, you're getting about 22 visits worth approximately $396/month in ad spend. Scale that across hundreds or thousands of keywords and you get your total traffic cost—often displayed in tools as "Traffic Value" or "Organic Traffic Cost." This metric matters because it quantifies SEO ROI in terms executives understand. A local service business showing $12,000/month in traffic cost demonstrates they're receiving the equivalent of a substantial paid ad budget without ongoing spend. It's particularly useful when comparing SEO investment to PPC alternatives or justifying continued optimization work. The number comes with caveats. CPC data pulls from Google Ads auction prices, which fluctuate by season, competition, and geography. A keyword might show $25 CPC nationally but $8 in Ottawa specifically. Organic click-through rates differ from paid ads—branded searches convert differently than informational queries. Tools also estimate traffic rather than measuring it directly, so expect 15-30% variance from your actual Google Search Console data. At Ottawa SEO Inc., we reference traffic cost when pitching enterprise clients who run parallel paid campaigns, because it speaks their language. For a 500-domain portfolio, aggregate traffic cost helps prioritize which properties deserve development resources. But we never optimize purely for traffic cost—a $50,000/month traffic value means nothing if those visitors don't convert. Focus on revenue-driving keywords first, then use traffic cost as a secondary gauge of search visibility and competitive positioning against others in your market.