The verdict in three sentences
An investment bank in London whose site shows a 4.9 s LCP and a 410 ms INP sends the wrong signal to executives browsing on mobile between meetings, and loses rankings on its brand and expertise queries. A Core Web Vitals audit costs, as a 2026 order of magnitude, EUR 2,500 to 4,000 (about GBP 2,100 to 3,400), then fixes EUR 6,000 to 14,000 (about GBP 5,100 to 11,900), delivered in 5 weeks. The contractual target is LCP under 2.5 s and INP under 200 ms on 90% of pages, measured on real Chrome user data.
Where poor corporate site scores come from
M&A boutiques and financial advisory sites share a technical profile: a full-screen homepage video, « Selected transactions » pages loaded with logos, a heavy cookie consent tool, analytics and booking scripts, and sometimes a chat nobody uses. Each item seems harmless on its own; together they blow up rendering time.
| Common cause | Typical impact | Metric affected |
|---|---|---|
| Uncompressed 12 to 25 MB homepage video | +1.5 to 2.5 s | LCP |
| Poorly integrated consent manager | +200 to 600 ms | LCP, INP |
| 6 to 12 third-party scripts (analytics, tags, chat, booking) | +150 to 300 ms per interaction | INP |
| Web fonts not preloaded (3 to 5 weights) | +300 to 800 ms | LCP, CLS |
| Unsized PNG deal logos | Layout shifts | CLS |
| CMS theme with 1.5 MB of unused JavaScript | +100 to 250 ms | INP |
A two-step budget: audit, then fixes
The audit must rely on field data (CrUX report and Search Console), not just a lab Lighthouse score. It produces a list prioritized by gain and effort, with a price for each fix.
| Service | 2026 range (EUR excl. VAT) | Duration |
|---|---|---|
| Field and lab data audit, 20 templates analyzed | 2,500 to 4,000 | 1 week |
| Video loading rework (poster, AV1/WebM, lazy loading) | 1,000 to 2,000 | 3 to 5 days |
| Third-party script and tag manager cleanup | 1,500 to 3,500 | 1 week |
| Font and image optimization (AVIF, dimensions) | 1,000 to 2,500 | 3 to 5 days |
| JavaScript reduction and per-page code splitting | 2,000 to 5,000 | 1 to 2 weeks |
| Continuous monitoring and alerts | 500 to 1,000 | 2 days |
| Total fixes | 6,000 to 14,000 | 4 weeks after the audit |
The high end usually means a site on an old CMS where JavaScript cannot be trimmed without touching the theme. If the audit shows that more than 40% of the fix budget would go into the theme, a targeted technical rebuild becomes more cost-effective than stacking patches.
What to require in the brief
| Criterion | Before | Contractual target |
|---|---|---|
| LCP (75th percentile mobile) | 4.9 s | Under 2.5 s |
| INP (75th percentile mobile) | 410 ms | Under 200 ms |
| CLS | 0.18 | Under 0.1 |
| Pages rated « Good » in Search Console | 22% | 90% |
| Homepage weight | 8.4 MB | Under 1.5 MB |
| Third-party scripts loaded at startup | 11 | 3 maximum |
CrUX data is consolidated over a rolling 28 days: plan the final sign-off 4 weeks after the fixes go live, not the next day.
Mini case study
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
Charlotte, marketing partner at a 35-person M&A boutique in Mayfair, London, sees that only 22% of the site's pages are rated « Good » by Google. The EUR 3,200 audit identifies the homepage video and 11 third-party scripts as the main causes. The selected fixes cost EUR 9,800, so EUR 13,000 in total (about GBP 11,000). After 5 weeks, LCP drops to 2.1 s. The site used to bring in 40 qualified contact requests a year; a 15% increase means 6 more. If just one turns into a mandate with a EUR 150,000 success fee, the investment pays back more than ten times.
FAQ
Is a Lighthouse score enough to judge a site?
No, Lighthouse measures a lab simulation. Google uses real Chrome visitor data over 28 days, and a site can score 90 in Lighthouse while failing in the field.
Should we drop the homepage video?
Not necessarily. A cover image shown immediately, then a video compressed under 3 MB loaded after rendering, often keeps the visual effect with LCP under 2.5 s.
How long before Search Console shows the effect?
Allow 28 days after go-live for the data to update. Ranking gains then appear within 1 to 3 months on competitive queries.
Is a cookie consent manager compatible with good scores?
Yes, if it is loaded asynchronously and blocks scripts until the user consents. This improves both UK GDPR compliance and INP, with a typical gain of 100 to 300 ms.
Do we need a monitoring contract after the fixes?
Monitoring at EUR 150 to 300 a month stops every new marketing script from degrading scores. Without it, half the gains often vanish within a year.
Let's scope your project. Share your site URL and read access to Search Console: we will price the Core Web Vitals audit and fixes, with an indicative budget and a 5-week schedule. 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.
