SEO vs Paid Media: Which Delivers Better ROI?
"Should we invest in SEO or paid ads?" It's the question every growth-focused business asks, and the wrong framing leads to wasted budget.
At iNDEXHILL, we run both channels for clients. Here's the honest breakdown of costs, timelines, and ROI, so you can make the right call for your business.
Why 'SEO vs Paid' is the wrong question
Let's start with the uncomfortable truth: this isn't an either/or decision. The best-performing companies use both channels strategically. The real question is:
- Where should you start?
- How should you allocate budget?
- When does each channel make sense?
SEO and paid media serve different purposes in your growth engine. Paid provides immediate demand. SEO builds compounding, sustainable traffic. The right mix depends on your stage, runway, and competitive landscape.
Customer Acquisition Cost by Channel
Typical B2B SaaS CAC benchmarks (lower is better)
SEO delivers the lowest customer acquisition cost at £800 once organic traffic compounds (year 2+), compared to £1,400 for Meta Ads and £3,200 for LinkedIn Ads. Cold outbound (£2,800) and Google Ads (£1,800) sit in between — making SEO the clear long-term winner for B2B SaaS.
View full data table
| Channel | CAC (£) |
|---|---|
| SEO (Year 2+) | £800 |
| Meta Ads | £1,400 |
| Google Ads | £1,800 |
| LinkedIn Ads | £3,200 |
| Cold Outbound | £2,800 |
That said, let's break down the numbers honestly.
The real cost comparison
Paid media costs
Paid acquisition costs are straightforward but often underestimated:
- Media spend: £5,000-50,000+/month depending on scale
- Management fees: 10-20% of spend or £1,500-5,000/month retainer
- Creative production: £1,000-5,000/month for ads, landing pages
- Average B2B CPC: £3-15 on Google, £1-5 on Meta
- Typical B2B CPL: £50-200 for qualified leads
SEO costs
SEO costs are less linear but more predictable once established:
- Monthly retainer: £3,000-10,000/month for comprehensive SEO
- Content production: Often included or £500-2,000 per piece
- Link building: £1,000-5,000/month for quality acquisition
- Technical SEO: One-time audits £2,000-5,000 + ongoing
- CPL at scale: £10-50 for organic leads (once ranking)
The key difference: paid media costs scale linearly with volume. SEO costs stay relatively flat while traffic compounds.
Timeline reality check
This is where most businesses get frustrated, and where honest expectations matter most.
SEO vs Paid Media Timeline
What to expect from each channel over time
If you need leads next month, SEO alone won't save you. If you want sustainable growth over 2-5 years, SEO delivers unmatched ROI.
Long-term ROI analysis
Here's where the math gets interesting. Let's model a £10,000/month marketing budget over 24 months:
Cumulative Leads Over 24 Months
£10,000/month marketing budget comparison
- Paid Only
- SEO Only
- Combined
Over 24 months with a £10,000/month budget, SEO delivers 3,000 cumulative leads versus paid media's 2,400 — a 25% advantage driven by compounding organic traffic. A combined strategy outperforms both, reaching 3,200 leads by month 24 as paid fills the gap while SEO builds momentum in the first 6 months.
View full data table
| Month | SEO Only | Paid Only | Combined |
|---|---|---|---|
| M1 | 0 | 100 | 60 |
| M3 | 20 | 300 | 200 |
| M6 | 150 | 600 | 450 |
| M9 | 400 | 900 | 750 |
| M12 | 800 | 1,200 | 1,100 |
| M18 | 1,800 | 1,800 | 2,000 |
| M24 | 3,000 | 2,400 | 3,200 |
Based on typical B2B: £100 CPL paid, £30 CPL organic at scale, 5% close rate
Scenario A: 100% Paid Media
- Total spend: £240,000
- At £100 CPL: 2,400 leads
- At 5% close rate: 120 customers
- CAC: £2,000 per customer
- Month 25 reality: Stop spending, traffic stops
Scenario B: 100% SEO
- Total spend: £240,000
- Months 1-6: Minimal leads (building foundations)
- Months 7-24: Compounding traffic, approximately 3,000 leads
- At 5% close rate: 150 customers
- Blended CAC: £1,600 per customer
- Month 25 reality: Traffic continues without spend
Scenario C: 60% Paid / 40% SEO (Our recommendation)
- Paid delivers immediate pipeline while SEO builds
- Gradually shift budget as organic traffic grows
- Year 2: 40% paid / 60% SEO
- Combined leads: approximately 3,200
- Blended CAC: £1,500 per customer
- Month 25 reality: Reduced paid spend, organic carrying majority
Budget allocation by stage
How you split budget depends entirely on your business stage and goals. Here's our recommended framework:
Recommended Budget Allocation
Year 1: Build pipeline while establishing organic foundations
- Paid Media
- SEO
- Testing
In year 1, paid media takes 60% of budget to fill the pipeline immediately while SEO (30%) builds organic foundations. A 10% testing allocation funds A/B tests and channel experiments.
View full data table
| Channel | Allocation (%) |
|---|---|
| Paid Media | 60% |
| SEO | 30% |
| Testing | 10% |
Recommended Budget Allocation
Year 2: Shift budget as SEO traffic compounds
- SEO
- Paid Media
- Testing
By year 2, SEO takes 50% of budget as compounding organic traffic lowers CAC. Paid media drops to 40% for retargeting and high-intent campaigns, with 10% reserved for ongoing testing.
View full data table
| Channel | Allocation (%) |
|---|---|
| SEO | 50% |
| Paid Media | 40% |
| Testing | 10% |
When to prioritise each channel
Prioritise Paid Media when:
- You need leads in the next 30-90 days
- Testing new markets, offers, or messaging
- Launching a new product or service
- Short runway and need immediate revenue
- Competitive keywords have 12+ month ranking timelines
Prioritise SEO when:
- You have 6-12 months of runway to invest
- Your market has consistent search demand
- Content and thought leadership align with your brand
- You want to reduce long-term CAC
- Competitors are winning organic and you're not
Run both when:
- You have budget for sustainable investment in both
- You want short-term pipeline AND long-term growth
- You're in a competitive market where both matter
- You want to use paid data to inform SEO content strategy
Common mistakes in channel allocation
We see these patterns consistently lead to poor ROI:
- Killing SEO after 3 months: SEO compounds. Stopping before month 6 wastes everything you've invested.
- Scaling paid without conversion optimisation: More traffic to a broken funnel just burns money faster.
- Treating channels as silos: Paid data informs SEO. SEO content supports remarketing. They work together.
- Chasing vanity metrics: Traffic and impressions don't matter. Revenue and CAC matter.
- Not tracking attribution properly: Multi-touch attribution is messy but essential. First-click and last-click both lie.
The businesses that win understand that marketing is portfolio management, not a single bet.
How we do this at iNDEXHILL
Our SEO & Organic Growth services are built around this exact framework, designed for businesses that need predictable growth.
See how we applied this approach in our client case studies.
Frequently Asked Questions
Want help implementing this?
If you're looking to scale organic growth, we offer a free SEO audit to identify quick wins and growth opportunities.
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