The True Cost of a Slow Online Shop — A Calculation

If your online shop makes €300,000 a year and your mobile site takes 5 seconds to load, you’re leaving roughly €30,000-50,000 on the table annually.

That’s not a scare tactic. It’s arithmetic.

The speed-revenue connection

The research on this has been consistent for years. Google’s own data: 53% of mobile visitors abandon a page that takes more than 3 seconds to load. Deloitte and Google published a study, Milliseconds Make Millions, showing that a 0.1 second improvement in mobile load time increases retail conversion rates by 8.4%.

These numbers come from aggregating millions of sessions across real e-commerce sites. They’re not theoretical.

The average mobile PageSpeed score across the 28 Magento shops I audited in Tirol was 55 out of 100. That typically corresponds to mobile load times of 4-8 seconds. Most of those shops are on the wrong side of the 3-second abandonment threshold for a significant portion of their mobile visitors.

And mobile is where most of the traffic is. Somewhere between 60-70% of e-commerce visits happen on a phone.

The back-of-napkin calculation

Here’s the model. Plug in your own numbers.

Annual online revenue:              €300,000
Current conversion rate:            2.0%
Monthly visitors:                   25,000

Current mobile load time:           ~5 seconds
After optimisation / Hyvä:          ~2 seconds

Expected conversion improvement:    15-25%
New conversion rate:                2.3-2.5%

Additional annual revenue:          €45,000-€75,000

Investment (Hyvä migration):        €15,000-€20,000
Payback period:                     3-5 months

These are conservative estimates. Some shops see 30-50% conversion improvements after significant performance work. The numbers above assume 15-25%.

Scale it up

The same logic at different revenue levels:

The bigger the shop, the more expensive every slow second is. A shop doing €1M a year with a 5-second mobile load time and a 2% conversion rate is not a small problem.

The costs you don’t see on the invoice

The direct conversion impact is the obvious one. But there are compounding effects.

Search rankings. Google has included Core Web Vitals as a ranking signal since 2021. A slower site ranks lower. Lower ranking means less organic traffic. Less organic traffic means either more ad spend to compensate or simply fewer visitors. The performance gap compounds over time as slower sites slide further in search results while faster competitors move up.

Customer acquisition cost. If your organic traffic is declining because your PageSpeed scores are dragging your rankings down, you need to spend more on paid acquisition to maintain visitor numbers. The cost shows up in your ad budget, not in your site performance report. But the cause is the same.

Brand perception. Customers who land on a slow mobile site and leave don’t send you a feedback form explaining why. They just don’t come back. Slow equals unprofessional in the instinctive calculus of a mobile user who’s comparing you to competitors on the same device.

Mobile-first indexing. Google doesn’t just use your mobile performance as one signal among many. It literally indexes your site based on the mobile version. The desktop experience barely matters for rankings anymore.

What "fast" actually means in 2026

Google’s Core Web Vitals targets:

• LCP (Largest Contentful Paint): under 2.5 seconds. The main content should be visible quickly.
• INP (Interaction to Next Paint): under 200ms. Clicks and taps should feel immediate.
• CLS (Cumulative Layout Shift): below 0.1. Elements shouldn’t jump around as the page loads.

For mobile PSI score: aim for 90+. The average across the Tyrolean shops I measured was 55. The shops that had migrated to Hyvä were at 90+.

The data from 303 shops across the region suggests this isn’t a problem unique to Magento or to Tirol. It’s the default state of e-commerce shops that haven’t specifically invested in performance.

The investment vs. the cost of doing nothing

Performance optimisation (quick wins):      €2,500-€5,000
Hyvä migration (full frontend rebuild):     €12,000-€25,000
Doing nothing for 12 months:                €15,000-€75,000 in lost revenue

The most expensive option is the one that looks free.

A shop doing €300,000 a year with the performance profile described above is already losing €45,000+ annually compared to what it would make with a properly optimised mobile experience. That loss is happening whether or not anyone notices it. There’s no invoice, so it doesn’t feel like spending.

But it is spending. It’s just invisible.

PageSpeed Insights will give you your actual score in 30 seconds. If the number makes you uncomfortable and you want to understand what it would take to move it, feel free to get in touch.