Quoting performance work is harder than quoting a build. The scope is invisible until you open the site, and clients compare you with a $99 plugin install. This is the process I use to keep quotes honest.
1. Never quote before a look
I ask for the URL and run PageSpeed Insights on three pages: home, one money page (service or product) and checkout if it is a store. Five minutes of testing tells me whether the problem is images, scripts, hosting or the database.
2. Sort the findings into three buckets
- Quick wins: oversized images, missing lazy loading, no cache headers
- Medium work: render-blocking scripts, unused CSS, plugin conflicts
- Structural: weak hosting, a heavy page builder, custom code that queries the database on every request
The price follows the buckets. A site with only quick wins is a small fixed-price job. A site with structural problems needs a conversation about hosting or a rebuild before any optimization.
3. Put the exclusions in writing
For stores I list the pages that must never be cached: cart, checkout, account. I also list which third-party scripts I will not remove without approval, such as chat widgets and ad pixels, since the client owns that decision.
4. Work on a copy
Backup first, staging when possible. Database cleanup and script deferral are the two changes most likely to break something quietly.
5. Deliver numbers, not a promise
I send a before-and-after report for each tested page. I do not promise a score, because lab results change between runs. I promise the specific fixes and the measured result.
6. Say no when it is not a speed problem
If the server is slow on a bare page, the honest advice is a hosting change. If the field data already passes, the honest advice is to leave it alone.
Typical ranges I see in the market for one-time projects: about $150 to $500 for small business sites, $500 to $1,500 for WooCommerce stores and $1,500 to $4,000+ for large custom stores. The breakdown, with a comparison checklist, is in the full guide: https://amanurrahman.com/blog-post/wordpress-speed-optimization-cost
What do you put in your performance quotes that most clients forget to ask about?