The verdict in three sentences
A 5-second LCP and a 68% bounce rate on an ageing WordPress B2B site destroy conversion and rankings. A performance rebuild on Next.js or Astro (10,000-16,000 EUR, 6-9 weeks) targets an LCP under 2.5 s and an INP under 200 ms. The expected return: +15 to +25% organic traffic and +12 to +20% form conversion over 6 months, sharply lowering cost per lead.
Before / after: the metrics that matter
Core Web Vitals are not just a score: they drive Google ranking and mobile bounce rate.
| Metric | Before (WordPress) | Target (Next.js/Astro) |
|---|---|---|
| LCP | 5.0 s | < 2.5 s |
| INP | 380 ms | < 200 ms |
| CLS | 0.24 | < 0.1 |
| Bounce rate | 68% | 45-50% |
| Mobile PageSpeed score | 38 | 90+ |
| Homepage weight | 4.2 MB | < 1.2 MB |
| Time to Interactive | 8.1 s | < 3.5 s |
Moving to static/SSR rendering and optimized images (WebP/AVIF) explains most of the gain.
Cost per lead: the real budget argument
A performance rebuild is justified in pipeline euros, not in a technical score.
| Metric | Before | After (6 months) |
|---|---|---|
| Organic traffic/month | 3,400 | 4,250 (+25%) |
| Form conversion rate | 1.3% | 1.6% (+20%) |
| Leads/month | 44 | 68 |
| Rebuild budget (EUR) | - | 13,000 |
| Cost per lead (12 months) | 41 EUR | 21 EUR |
| Additional leads/year | - | +288 |
At a 15,000 EUR average B2B deal and a 15% close rate, +288 leads/year represent over 40 additional potential contracts.
Mini case study
Conor, digital lead of an industrial-trading SME in Dublin (2017 WordPress site), sees a 5.1 s LCP and a 71% mobile bounce rate. An Astro rebuild at 12,500 EUR, delivered in 8 weeks: LCP down to 1.9 s, mobile PageSpeed 94. Over 6 months, organic traffic gains 22%, form conversion 18%, and cost per lead falls from 43 to 22 EUR. The extra leads fund the rebuild in under 4 months.
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FAQ
Why is my WordPress site slow?
Plugin bloat, heavy theme, unoptimized images and no cache/CDN. An LCP over 4 s is common on these ageing stacks.
Next.js or Astro for a B2B corporate site?
Astro excels on mostly static sites (corporate, blog); Next.js if you have dynamic areas or app integration. Both reach an LCP under 2.5 s.
How much does a performance rebuild cost?
10,000 to 16,000 EUR in 2026 for a B2B corporate site, including image optimization, cache/CDN and a Core Web Vitals audit.
What realistic SEO gain?
+15 to +25% organic traffic over 6 months at equal content, thanks to Core Web Vitals ranking and lower bounce. Treat as a 2026 order of magnitude.
How long until results show?
Speed is immediate; SEO gains materialize over 3 to 6 months as Google re-indexes and re-evaluates.
Let's scope your project. Send us your URL and current PageSpeed scores, and we will quote a performance rebuild between 10,000 and 16,000 EUR with LCP/INP targets. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
