The verdict in three sentences
A custom B2B e-commerce platform costs between EUR 45,000 and 120,000 in 2026 depending on catalogue size, negotiated-pricing complexity and depth of ERP integration. Below EUR 30,000, stay on Shopify Plus or a packaged solution; once multi-buyer accounts and per-customer pricing dominate, a build pays back in 18 to 30 months. The real cost is not the licence, it is the business logic: credit limits, volume discounts, approval workflows.
What each line item costs in 2026
A B2B platform budget breaks down by functional block. Here is a 2026 order of magnitude for a mid-size project (5,000 to 20,000 SKUs, 200 to 800 buyer accounts).
| Line item | Scope | Budget EUR |
|---|---|---|
| Foundation & design system | UX, front, back, CI/CD | 14,000 - 28,000 |
| PIM & catalogue | Products, variants, media | 8,000 - 18,000 |
| Per-customer pricing | Price lists, volume tiers | 7,000 - 16,000 |
| Multi-buyer accounts | Roles, budgets, approval | 5,000 - 12,000 |
| ERP integration | Stock, price, order sync | 9,000 - 24,000 |
| Payment & credit | Card, transfer, 30/60 days | 4,000 - 10,000 |
| UAT & go-live | Testing, migration, training | 6,000 - 14,000 |
SaaS licence vs build: the 3-year total
Total cost of ownership often inverts intuition. Over three years, a premium SaaS stacks licence, paid apps and platform fees.
| Scenario | Yr 1 | Yr 2 | Yr 3 | 3-year total |
|---|---|---|---|---|
| Shopify Plus B2B | 24,000 | 24,000 | 24,000 | 72,000 |
| + apps & % fees | +9,000 | +11,000 | +13,000 | +33,000 |
| Custom build | 75,000 | 18,000 | 18,000 | 111,000 |
| Build (maintenance only) | 21,600 | 21,600 | 21,600 | 64,800 |
At constant volume SaaS stays competitive; once platform fees (2% outside the native gateway) erode margin on revenue above EUR 3M, custom pulls ahead. RGPD-compliant OVH/Scaleway hosting: EUR 200 to 600/month depending on load.
Mini case study
Bruno, e-commerce director at an industrial-supplies distributor in London, runs 12,000 SKUs and 340 reseller accounts with per-customer price lists. On Shopify Plus, platform fees plus six apps reached EUR 41,000/year on EUR 4.2M revenue. A custom build at EUR 82,000, amortised via EUR 1,600/month maintenance, cuts annual cost to EUR 19,200 from year two: roughly EUR 21,800/year saved and pricing rules finally native, with no third-party app.
FAQ
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How long to deliver a custom B2B platform?
Expect 12 to 20 weeks in 2026: 3 to 4 weeks of discovery and design, 7 to 12 of development, 2 to 4 of UAT and data migration. A catalogue above 20,000 SKUs adds 2 to 3 weeks.
What day rate applies?
The 2026 day rate for a senior team (developer, tech lead, UX) sits between EUR 550 and 750. An EUR 82,000 project represents roughly 120 to 145 person-days.
Can we keep our existing ERP?
Yes, integration runs through API or middleware. Budget EUR 9,000 to 24,000 depending on the ERP (SAP, Sage, Odoo) and how often stock and prices sync.
What maintenance budget should we plan?
2026 maintenance ranges from EUR 900 to 2,500/month depending on SLA, covering fixes, minor evolutions, monitoring and security updates. Add hosting at EUR 200 to 600/month.
At what revenue does custom become worthwhile?
Generally above EUR 3M annual e-commerce revenue, or once per-customer pricing and multi-buyer accounts become central. Below that, a SaaS gives the best ratio.
Let's scope your project. Tell us about your catalogue, pricing rules and ERP: we will define the scope, an indicative budget (EUR 45,000 to 120,000) and a 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.
