The short answer: inbound is compounding. Outbound is a launch vehicle. But the nuance matters, because the right answer depends entirely on where you are in the business lifecycle.
The CAC data#
Across a 939-company B2B sample from Q1 to Q3 2025, the numbers are stark. Inbound CAC averages $89. SEO specifically comes in at $31 cost per lead. Email at $53. Webinars at $72. Outbound, when you model it efficiently, runs $267 to $400. Fully loaded with the real cost of business development rep salaries, tooling, data licences, and management overhead — it climbs to $1,980. Paid ads average $181 cost per lead. Trade shows and events run $412 to $811.
The inbound advantage isn't just the headline number — it's what happens to it over time. SEO compounds. The cost per acquired customer drops as the content portfolio matures. Outbound doesn't compound — the cost structure is relatively fixed to headcount. Scale outbound by 2x and your cost roughly doubles. Scale inbound by 2x and you're adding to a compounding asset.
The optimal channel mix#
High-performing B2B companies in 2025 ran roughly: 30% inbound, 25% partnerships, 20% paid, 15% outbound, 10% events. Companies that allocated 40 to 50% of budget to inbound plus partnerships saw approximately 30% lower overall CAC compared to outbound-heavy peers.
When outbound makes sense#
Outbound is critical in the early stage — pre-product-market-fit, sub-$2 million ARR. When you don't yet have content ranking, community built, or brand recognition, outbound is how you learn what messaging resonates. It loses economic logic as companies scale beyond $10 million ARR, at which point events and inbound take over in the channel mix of top performers.
The other variable: ACV. Outbound only works economically when the average contract value justifies the cost per acquisition. If your ACV is under $10,000, the math of a fully-loaded outbound motion usually doesn't close. Below that level, double down on inbound and partnerships.
The 2025–2026 shift#
Events and in-person interactions dominated the GTM channel mix in 2025 for companies above $10 million ARR. SEO and content strengthened as scalable growth levers at earlier stages. AI-enabled inbound — automated lead qualification, predictive scoring, behaviour-triggered nurturing — is compressing time-to-conversion by 20 to 30% for teams that have implemented it properly.
The inflation problem#
Average B2B CAC has risen 222% over the last eight years. Median CAC payback period for B2B SaaS sits at 15 months. Companies anchored to outbound-heavy channel mixes are seeing steeper CAC inflation than inbound-heavy peers — because outbound costs scale with headcount and data costs, both of which have risen. Inbound costs scale with content quality, which holds its value better.
The takeaway: inbound compounds, outbound launches. Companies still relying on outbound past $10 million ARR are watching their CAC payback period extend toward 24 months and beyond — and losing the efficiency battle to competitors who built the inbound flywheel two years earlier.