Warehouse management system for an ecommerce 3PL: custom or vendor

The verdict in three sentences

For an ecommerce 3PL in Venlo, Tilburg or the Midlands shipping 8,000 orders a day for 45 brands, the WMS decision depends less on location management, which every vendor handles, than on activity-based billing and store connectors. A vendor WMS costs, as a 2026 order of magnitude, 1,500 to 6,000 EUR (£1,300 to £5,200) a month plus integration, while a custom build from Kolonell sits between 2,500,000 and 15,000,000+ FCFA (3,810 to 22,870+ EUR) over 5 to 8 months. The best answer is often hybrid: keep a proven WMS for the warehouse floor and build the client, billing and connector layer.

What a 3PL really has to control

Whether in the Dutch logistics corridor or the UK golden triangle, ecommerce 3PLs compete on three metrics: same-day dispatch for orders before 3 pm, picking error rate and the accuracy of each brand's invoice.

At 8,000 orders a day, moving from 0.8 % to 0.3 % errors removes 40 errors daily. At an average 15 EUR (about £13) per error for returns, reshipping and goodwill, savings exceed 150,000 EUR a year.

Vendor, custom or hybrid

For a warehouse this size, rebuilding stock, replenishment and wave picking logic is risky. Billing, however, is where vendors are weakest and where every 3PL has different rules: inbound per pallet, storage per cubic metre, pick per line, special packaging, returns, kitting.

The activity-based billing module

It is often the first project to launch. It reads WMS movements, applies each brand's rate card and produces a detailed invoice the client can check in a portal.

• Inbound: per pallet, carton or unit, with a surcharge for non-compliant deliveries.
• Storage: per cubic metre or per location, calculated daily.
• Picking: flat fee per order plus a price per extra line.
• Shipping: carrier recharge with a configurable margin.
• Returns: inspection, restock or disposal.

At Kolonell, a billing and client portal layer falls in the medium bracket, 4,000,000 to 7,000,000 FCFA (6,100 to 10,670 EUR). Less common store connectors and hosting are quoted separately.

Mini case study

Sarah, COO of a 3PL near Rotterdam, invoices 45 brands. Month-end close takes two controllers 5 days and 4 % of lines are disputed, on monthly revenue of 600,000 EUR.

• Disputes: 4 % × 600,000 = 24,000 EUR a month contested, about a third eventually written off, so 8,000 EUR lost a month.
• With automated billing at 0.8 % disputes: 1,600 EUR lost a month.
• Gain: 6,400 EUR a month, 76,800 EUR a year, plus 8 person-days recovered each month.

A 9,500 EUR medium-bracket project with 114 EUR of monthly maintenance pays back in under two months. For a London 3PL the logic is the same in pounds.

FAQ

Do we need to replace our WMS to add custom billing?

No, if your WMS exposes movements by API or daily export, which most recent vendors do. The layer plugs in within 3 to 5 months.

How much does a store connector cost?

The common ones (Shopify, WooCommerce, Magento) take 1 to 3 weeks each. Each connector is quoted separately depending on order volume and sync rules.

Can brands see their stock live?

Yes, the client portal shows available stock, open orders and the provisional monthly invoice, refreshed nightly or in real time depending on the WMS.

What about Black Friday peaks?

The billing layer must absorb 3 to 4 times normal volume, over 30,000 orders a day. The architecture is sized and load tested before November.

Can we start small?

Yes. A first release limited to billing and the portal falls in the simple bracket, 2,500,000 to 4,000,000 FCFA (3,810 to 6,100 EUR), with connectors following.

Let's scope your project. We audit your current WMS, rate cards and connectors, then propose the most profitable scope with a phased plan. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.