The verdict in three sentences
In London in 2026, a custom B2B marketplace costs GBP 60,000 to 150,000 one-off, versus GBP 180 to 450/month for a SaaS like Sharetribe with customization limits. SaaS lets you test fast and cheap, but it caps out on split payments, bespoke commissions and payment-provider integration. Once volume takes off and commission generates revenue, custom regains the economic edge and gives full control over the money flow.
Custom vs SaaS: the 2026 comparison
The right call is not just the sticker price. It depends on your need for control over payment, commissions and the seller experience.
| Criterion | SaaS (Sharetribe et al.) | Custom |
|---|---|---|
| Launch cost | GBP 6,000 - 18,000* | GBP 60,000 - 150,000 |
| Monthly cost | GBP 180 - 450 | GBP 250 - 800 (infra) |
| Automatic split payment | Limited | Full, bespoke |
| Native payment routing | Basic | Yes |
| Configurable commission | Basic | Unlimited, per category |
| Code ownership | No | Yes |
| Volume ceiling | Medium | High |
*SaaS setup and initial customization. SaaS stays relevant to validate a concept before investing in custom.
Split payment and commissions
The heart of a marketplace is the money flow: charge the buyer, pay out the seller, retain the commission. Reliable split payment is what earns seller trust.
| Element | 2026 operation |
|---|---|
| Buyer charge | Card / wallet / bank |
| Platform commission | 5-20% configurable per category |
| Seller payout | 80-95% of the amount |
| Payout frequency | Weekly, automatic |
| Example: GBP 1,000 order | GBP 850 seller / GBP 150 platform |
| Dispute handling | Funds held until resolution |
A generic SaaS handles bespoke split poorly; custom integrates it natively, which is often decisive.
The 3-year total cost
With volume, the comparison flips. Commission funds the custom build, while SaaS takes a percentage or imposes rising subscription tiers.
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| Scenario (3 years, rising volume) | SaaS | Custom |
|---|---|---|
| Initial cost | GBP 12,000 | GBP 100,000 |
| Subscriptions/fees 36 months | GBP 45,000 | GBP 70,000 (infra + upgrades) |
| Platform transaction fees | GBP 30,000* | GBP 0 (collect directly) |
| Customization limits | High | None |
| 3-year total | GBP 87,000 | GBP 170,000 |
*Some SaaS take a % of GMV. At high volume, this cost quickly exceeds the custom investment, which becomes more profitable beyond a certain transaction threshold.
Mini case study
James, a founder in London, launches a B2B marketplace for restaurant supplies. He starts on a SaaS at GBP 12,000 setup to validate demand in 4 months. With traction confirmed (180 sellers, GBP 90,000 monthly GMV), he switches to custom at GBP 110,000 with native split payment and a 12% commission. On that GMV, his commission generates GBP 10,800/month, i.e. GBP 129,600/year: the custom platform is paid back in 15 months while removing GMV fees and SaaS limits.
FAQ
Should I start with SaaS or go straight to custom? If the idea is unproven, a SaaS at GBP 6,000-18,000 tests demand risk-free. If the model is proven or expected volume is high, custom avoids a costly migration.
Why is split payment so important? Because it drives seller trust and your revenue. Reliable split with weekly payout is a major competitive advantage.
What commission rate to target? Between 5 and 20% depending on category and added value. A B2B marketplace often sits between 8 and 15%, adjustable per product type.
How long to build a custom marketplace? Plan 4 to 8 months depending on scope. Split payment, seller moderation and dispute handling are the most technical parts.
At what volume does custom become profitable? Once monthly commission clearly exceeds infra cost and SaaS GMV fees eat your margin, typically beyond GBP 60,000-90,000 of monthly GMV.
Let's scope your project. Tell us your category, target volume and commission model, and we cost SaaS or custom for your stage. 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.
