The verdict in three sentences
Replatforming a B2B e-commerce site in 2026 costs between 30,000 and 90,000 EUR depending on catalog size, number of customer accounts and the complexity of pricing rules. The real risk is not technical but commercial: a poorly prepared cutover can drop revenue by 15 to 40 % for several weeks. The right method favors a progressive migration with controlled SEO redirects rather than a Friday-night big bang.
Why and when to migrate
A platform becomes a liability when maintenance cost exceeds the cost of an amortized rebuild. The signals: load times above 3 seconds, inability to add a payment method or a per-customer pricing rule, single-vendor lock-in, and a back office your sales team hates.
| Migration item | 2026 range (EUR) | Indicative timeline |
|---|---|---|
| Scoping + catalog migration (< 5,000 SKUs) | 6,000 - 14,000 | 3-5 weeks |
| Customer accounts + negotiated pricing | 5,000 - 12,000 | 2-4 weeks |
| Platform build (design + checkout) | 15,000 - 45,000 | 8-16 weeks |
| SEO redirect plan (301) | 2,500 - 6,000 | 1-2 weeks |
| QA + order history migration | 4,000 - 10,000 | 2-4 weeks |
| Team training + assisted go-live | 2,500 - 6,000 | 1-2 weeks |
Expect a 4 to 7 month project between kick-off and a fully stabilized platform.
Big bang or progressive migration
The cutover strategy weighs more on risk than on the budget itself. A big bang concentrates risk on a single night; a progressive migration spreads it but runs two systems in parallel.
| Criterion | Big bang | Progressive migration |
|---|---|---|
| Cutover duration | 1 night / weekend | 4 to 10 weeks |
| Revenue-drop risk | High (15-40 %) | Controlled (< 10 %) |
| Dual-run cost | None | +8-15 % of budget |
| Rollback possible | Difficult | Yes, per batch |
| Best for | Simple catalog | Complex catalog and clients |
For a B2B store with per-customer negotiated pricing, progressive migration (by product family or customer segment) stays safest. You cut over a pilot segment first, measure conversion, then generalize.
The SEO trap
A B2B migration loses on average 20 to 30 % of organic traffic in the first three months if the redirect plan is rushed. Every old URL must 301 to its equivalent, canonical tags must be checked, and the sitemap resubmitted. Plan a crawl audit before and after, and watch Search Console for 90 days.
Mini case study
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Marc runs an industrial-supplies distributor in Nantes: 8,400 SKUs, 620 active customer accounts, 2.8 M EUR of online revenue. His 2018 platform crashes twice a month and blocks adding net-30 payment. Migration quote: 62,000 EUR, progressive migration over 5 months. Each outage cost him roughly 4,500 EUR in lost orders, about 108,000 EUR/year. The rebuild pays for itself in under 8 months, before counting the conversion gain (+0.9 pt) on the new platform.
FAQ
How long does a B2B migration actually take?
Expect 4 to 7 months for a 5,000-15,000 SKU catalog with negotiated pricing. A simple catalog under 1,000 SKUs can close in 3 months.
Can I keep my old platform as a fallback?
Yes, and it is recommended in progressive migration: you keep the old system read-only for 4 to 10 weeks, adding 8 to 15 % to the budget but cutting risk threefold.
What happens to my SEO after cutover?
With a clean 301 redirect plan, the loss is limited to 5-10 % for 6 to 8 weeks, then traffic recovers. Without a plan, drops of 20 to 30 % can persist.
Do I need to migrate all order history?
Not into the active database. You typically keep 24 months of history live and archive the rest, cutting migration cost by 20 to 40 %.
How do I avoid the revenue drop?
Progressive cutover by segment, go-live early in the week (never a Friday), reinforced support for the first 15 days, and real-time checkout monitoring.
Let's scope your project. Send us your SKU count, number of customer accounts and current platform, and we'll quote a progressive migration with an SEO plan. 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.
