The verdict in three sentences
Of the 40 issues in a typical audit, about ten account for 80% of the gain: hero images, third-party scripts, fonts and server rendering. Fixing them costs 3,000 to 12,000 EUR and reaches Google's thresholds: LCP under 2.5 s, INP under 200 ms, CLS under 0.1. After the fixes we observe on average 8 to 15% more leads, which often repays the work in under 6 months on a B2B site that generates quote requests.
Sorting the 40 audit issues by impact
A performance audit often mixes cosmetic warnings and structural causes. For a manufacturer's site in London with a product catalogue, PDF datasheets and a quote form, these are the fixes to handle first:
| Fix | Target metric | Typical gain | 2026 cost |
|---|---|---|---|
| Hero image in AVIF or WebP, preloaded and sized | LCP | − 0.8 to − 1.5 s | 400 to 1,200 EUR |
| Removing or deferring third-party scripts (chat, maps, pixels) | INP, LCP | − 100 to − 250 ms INP | 600 to 2,000 EUR |
| Self-hosted fonts with font-display swap | LCP, CLS | − 0.2 to − 0.5 s | 300 to 800 EUR |
| Reserved space for cookie banners and visuals | CLS | from 0.25 to under 0.05 | 300 to 900 EUR |
| JavaScript splitting and unused module removal | INP | − 80 to − 200 ms | 1,200 to 4,000 EUR |
| Server cache and CDN | TTFB, LCP | − 0.3 to − 0.9 s | 500 to 2,000 EUR |
| Replacing the home carousel with a static image | LCP, INP | − 0.4 to − 1 s | 400 to 1,100 EUR |
What the work costs depending on the site
The budget depends mainly on the technology. A WordPress site loaded with plugins is quick to fix, whereas a proprietary theme or an old framework sometimes needs the template rebuilt.
| Situation | Audit | Fixes | Timeline | Expected result |
|---|---|---|---|---|
| WordPress, 30 to 80 pages, 15 to 25 plugins | 1,500 EUR | 3,000 to 5,000 EUR | 2 to 3 weeks | LCP 1.8 to 2.4 s |
| WordPress with a heavy page builder | 2,000 EUR | 5,000 to 8,000 EUR | 3 to 5 weeks | LCP 2 to 2.5 s |
| Proprietary CMS or old framework | 3,000 EUR | 7,000 to 12,000 EUR | 4 to 6 weeks | LCP 2 to 2.5 s, INP under 200 ms |
| Poorly configured Next.js or similar | 2,500 EUR | 4,000 to 9,000 EUR | 3 to 4 weeks | LCP under 1.8 s |
| Multilingual site with 2,000 product pages | 4,000 EUR | 8,000 to 12,000 EUR | 5 to 7 weeks | 75% of URLs green |
| Monthly Core Web Vitals monitoring | included | 250 to 600 EUR a month | ongoing | thresholds maintained |
Google's field data (CrUX report) updates over a rolling 28 days: allow 4 to 6 weeks before Search Console shows URLs as green, and 2 to 3 months to measure the traffic effect.
Linking performance to leads
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A 22% drop in organic traffic is not always explained by speed alone: also check Google updates and deindexed pages. Speed, however, acts directly on conversion. On mobile, each second saved on LCP reduces bounce rate by 7 to 12% on the B2B sites we track. So measure the quote form conversion rate before and after, over 8 weeks.
Mini case study
James, marketing manager at an industrial equipment manufacturer in London, receives 60 quote requests a month with a 15% close rate and an average order of 9,000 EUR. His site shows a mobile LCP of 4.6 s and an INP of 420 ms. He invests 2,000 EUR in the audit and 7,000 EUR in fixes, 9,000 EUR in total. With 10% more leads he gains 6 requests a month, so 0.9 orders, or 8,100 EUR of extra monthly revenue. At a 30% margin, the work pays back in about 4 months.
FAQ
Do we need a full redesign to go green? Rarely: in 7 cases out of 10, targeted fixes are enough. A redesign makes sense if the site is over 7 years old and fixes exceed 12,000 EUR.
Why does PageSpeed show a different score from Search Console? PageSpeed tests in the lab on a simulated phone, Search Console aggregates real visits over 28 days. Only real-user data counts for ranking.
Has INP really replaced FID? Yes, since March 2024 INP is the official responsiveness metric. It measures all interactions and the 200 ms threshold is still the reference in 2026.
Must marketing scripts go? No, load them after consent and after rendering. A well-configured tag manager cuts their impact by 50 to 70%.
How long do the gains last? Without monitoring, a site loses its gains in 6 to 12 months as features are added. Monthly monitoring at 250 to 600 EUR keeps the thresholds.
Let's scope your project. Send us your audit and site URL: we will prioritise the fixes, price the work between 3,000 and 12,000 EUR and set a 2 to 7 week timeline. 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.
