The verdict in three sentences
Optimising a B2B site's Core Web Vitals costs between 3,000 and 12,000 EUR in 2026 depending on the scope and existing technical debt. The 2026 targets to pass are an LCP under 2.5 s, an INP under 200 ms and a CLS under 0.1 on mobile. The ROI is twofold: +5 to +10 % conversion per second saved on load, and better mobile ranking that mechanically lifts SEO traffic.
The 2026 targets and the levers to hit them
Since INP replaced FID, interface responsiveness now weighs as much as display speed. Each metric has its own levers, and the budget depends mainly on how deep you go into code and infrastructure.
| Metric (2026 target) | "Good" threshold | Main levers |
|---|---|---|
| LCP (Largest Contentful Paint) | < 2.5 s | AVIF/WebP images, preload, CDN, hosting |
| INP (Interaction to Next Paint) | < 200 ms | Code splitting, JS reduction, web workers |
| CLS (Cumulative Layout Shift) | < 0.1 | Media dimensions, fonts, space reservation |
| TTFB (server) | < 800 ms | Cache, CDN, back-end optimisation |
A prior performance audit (often included in the quote) measures the gap between the current state and these thresholds before any commitment.
Price by scope
Optimising a few images has nothing to do with reworking an application's JavaScript rendering. Here are the tiers observed in 2026.
| Intervention level (2026) | Content | Price EUR | Timeline |
|---|---|---|---|
| Light optimisation | Images, cache, lazy loading | 3,000 – 5,000 | 1-2 weeks |
| Medium optimisation | + CDN, code splitting, fonts | 5,000 – 8,000 | 2-4 weeks |
| Heavy optimisation | + render rework, SSR/hydration, hosting | 8,000 – 12,000 | 4-8 weeks |
| Monthly performance monitoring | Monitoring, perf budget | 400 – 900 /month | Ongoing |
Always demand a documented before/after measurement (PageSpeed, CrUX, field data) to make the paid gain objective.
Mini case study
Thomas, e-commerce manager at a B2B supplies distributor in Bordeaux, sees a 4.3 s mobile LCP and a 1.8 % conversion rate. He invests 6,500 EUR in a medium optimisation (AVIF, CDN, code splitting) that brings LCP to 2.2 s, saving 2.1 s. On 40,000 sessions/month and a 180 EUR average basket, a +12 % conversion gain (from 1.8 % to 2.0 %) generates about 144 extra sales/month, i.e. 25,900 EUR of additional monthly revenue. The investment pays back in under a week of surplus.
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FAQ
Why did INP replace FID in 2024?
Because INP measures responsiveness across the whole visit, not just the first interaction. In 2026, an INP > 200 ms hurts experience and mobile ranking.
Is a good Core Web Vitals score enough to rank?
No, it's one factor among many, but a tie-breaker: with comparable content, the fast site wins. It's mostly a conversion lever.
Is Lighthouse data enough?
No, Lighthouse gives lab data; Google relies on field data (CrUX) from real users. You must track both.
Do I need to change hosting?
Sometimes. A TTFB above 800 ms drags LCP down whatever the front-end optimisation; a CDN or faster hosting then becomes unavoidable.
How long does the gain last?
Without discipline, performance degrades with every new feature. A performance budget and monthly monitoring (400-900 EUR) protect the gains.
Let's scope your project. Send us the URL to optimise and your current scores: we measure the gap to 2026 targets and cost the work. 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.
