guide · custom_erp
Custom ERP for SMEs: what it costs, what it returns
Does your case really justify going custom, how much does it cost, what return on investment? Honest, numbers-backed answers, with no jargon.
2 ERPs in production · price fixed at signing
Does your SME really need a custom ERP?
Before we talk budget, let’s talk need. A custom ERP only makes sense if your business has a real specificity — not to do what everyone else does. Here are the concrete signals I keep seeing at the SMEs for which custom becomes the right investment.
- You’re juggling 5 tools or more. Excel, Notion, Trello, HubSpot, Drive, an invoicing tool… the information is scattered and nobody has the full picture.
- Your teams are doing double data entry. The same data gets re-keyed from one tool to the next, which costs time and creates missed details and errors.
- Your processes are unique to your business. No off-the-shelf package really fits: you spend your time working around the tool rather than working with it.
- You’ve hit the ceiling. The patchwork still holds, but every new hire and every month of growth deepens the debt. It won’t survive the next step up.
If you tick three of these boxes, custom is worth studying. But let’s be clear about the reverse: if an off-the-shelf tool covers the bulk of your need, custom would be a pointless extra cost.
Custom, Odoo or off-the-shelf SaaS: the honest table
✅ a good fit · ⚠️ partial / variable · ❌ a poor fit. Off-the-shelf packages are designed for 80% of cases; custom exists for the 20% where your business is genuinely different.
| Criterion | Custom ERP | Odoo / off-the-shelf package | HubSpot / vertical SaaS |
|---|---|---|---|
| Genuinely specific business processes (your 20%) | Modelled exactly on your business | You bend your processes to fit the tool | Framework imposed by the vendor |
| Need 80% covered by the standard product | Pointless extra cost — I’d advise against it | The right choice, fast to deploy | The right choice if the module exists |
| Cost model | One-shot fixed price, paid once | Licence + integrator + maintenance | Per-seat subscription, recurring for life |
| Code ownership | 100% assigned from signing | Open-source but integrator lock-in | None — you rent the access |
| Time to production | 3 to 6 months for a full ERP | Fast off the shelf, slow if customised | A few weeks if it fits |
| Growth ceiling | Designed to scale with you | Custom modules costly to maintain | Per-seat cost that explodes at scale |
How much it costs
No hidden day rate, no surprise invoices: a fixed price, a price fixed at signing. Here are the ranges depending on the scale of the project. Most complete business ERPs land between €35k and €80k excl. VAT.
| Engagement | Price | When |
|---|---|---|
| Product Diagnostic | €1,500 excl. VAT (deducted if we continue) | You’re on the fence: 5 days to scope and cost it out |
| MVP Sprint | From €8k excl. VAT | First version in production in 3 to 5 weeks |
| Custom ERP build | From €25k excl. VAT · most often €35k–80k | Complete business tool, phased across 4 milestones |
How you pay: 4 milestones, not a blind cheque
The ERP fixed price is milestoned across 4 deliverables. Each approved milestone triggers the matching payment — and you can stop after a delivered milestone, with no penalty.
- 30%Deposit at kick-off
- 30%At mid-project
- 30%At delivery
- 10%At the end of the warranty
Tax benefit
An SME can recover 20% via the French Innovation Tax Credit (CII)
I’m an accredited CII provider, no. 27009163 (DRIEETS Île-de-France). In practice, if you’re an SME, 20% of what you entrust to me on the design of an innovative product can be refunded by the French government, within a limit of €400,000 of eligible spend per year. On a €50k ERP, that can represent up to €10k refunded.
Eligibility depends on the innovative nature of the project and is confirmed with your chartered accountant. As an accredited provider, I supply the traceability evidence (specification, deliverables, time spent) to secure your claim.
What it returns
The calculation is simple to set out. An off-the-shelf ERP like Salesforce with its add-ons costs €30k–80k a year, recurring — you pay for life, and you rent the access without ever owning anything. A custom ERP build is a one-shot fixed price of €35k–80k, paid once, with the code 100% assigned to you.
The result: the break-even point against a recurring licence lands in 12 to 18 months. Past that mark, every following year is a net saving, and you keep your independence — no vendor can raise its prices or cut off your access.
The cost of inaction, meanwhile, is invisible but real. A team losing a significant share of its time to double data entry and to manual syncing between tools means entire days burned every month — on top of the errors, the missed details, and the missed opportunities for want of the full picture. That cost grows as you grow.
A real case: the ERP of an event caterer
A fast-growing SME orchestrating around 500 catering projects a year with about twenty people. At first, operations ran on Excel and Notion. But volume kept climbing, the team grew, and the scattered tools created double entry and missed details. Seven scattered tools, and the team estimated it was losing close to 30% of its time on manual syncing. They needed a single business tool covering the whole cycle: leads, projects, quotes, event planning, suppliers, logistics, invoicing.
First phase: a first ERP built to move fast, a settled data model, core functions delivered module by module. Second phase: a clean migration to a modern code stack (Next.js + Supabase), switching all users over in a single step rather than running parallel environments. Eighteen months of historical data were migrated with no loss and no service interruption.
The result: one single tool instead of a patchwork of seven, a trained and self-sufficient team, and an architecture that supports scaling past 30 users. The code stack unlocks what the previous tool was capping — faster, further, and cheaper to run.
Same logic for a retirement-advisory firm: an internal ERP, a magic-link client portal and embedded business AI, consolidating the entire operation of advisers and closers into a single tool. See the retirement-firm case →
How it works, concretely
- 1
Discovery — 30 min, free
You walk me through your context. I tell you honestly whether I can help, whether I’m the right fit, and roughly what it might cost. If I’m not the right fit, I’ll point you elsewhere.
- 2
Product Diagnostic — €1,500, deducted afterwards
To go further without committing to a full engagement: 5 days of audit, a functional specification, a costed estimate, a recommended stack. The cost is 100% deducted if we continue together.
- 3
Scoping and sign-off — 1 to 2 weeks
We refine the scope together. You see exactly what the fixed price covers, what it doesn’t, and the price of each option. The quote gets signed when you’re ready, not before.
- 4
Build — 3 to 6 months depending on scope
Real-time tracking, weekly check-in, regular demos, documentation as we go. 4 payment milestones (30 / 30 / 30 / 10).
- 5
Delivery + 6-month bug warranty
Go-live, team training, a bug-fixing warranty for 6 months. Beyond that: a Care Pack or new features handled case by case.
As long as no quote is signed, you’re committed to nothing. Discovery and early conversations are 100% free.
Frequently asked questions
What is the price of a custom ERP for an SME?
From €25k excl. VAT, and most complete business ERPs land between €35k and €80k excl. VAT depending on complexity. It’s a one-shot fixed price, paid once, with the code 100% assigned to you. For comparison: an off-the-shelf ERP like Salesforce with its add-ons costs €30k–80k a year, recurring — the return on investment of going custom lands in 12 to 18 months.
Custom or Odoo / off-the-shelf solution?
Off-the-shelf packages are designed for 80% of cases. If your business processes are in the remaining 20%, you’ll spend more time forcing them to fit than actually using them, and custom is justified. If Odoo or HubSpot covers 80% to 90% of your need, I tell you so during scoping and I don’t take the project — it’s more honest and cheaper for you.
How long does it take to develop a custom ERP?
Count on 3 to 6 months for a complete business ERP, phased across 4 milestones: a first usable version, advanced modules, automations, then documentation. A first usable version arrives well before the end: you don’t wait six months to see something concrete. A tighter MVP Sprint ships in 3 to 5 weeks.
Does the code really belong to me?
Yes, 100%. The code and the rights are assigned to you by contract from signing, in a private repository your team can have read access to. The architecture documentation is delivered continuously, so that your team or another developer can take over maintenance at any time, without a hitch and without lock-in.
What happens after delivery?
Bug-fixing is guaranteed for 6 months after delivery, team training included (walkthrough videos and a live session). Beyond that, two options depending on your need: a Care Pack with regular presence, or a fixed price for new features, quoted case by case. Since the code is yours, you can also take the wheel in-house.
30 minutes to cost out your case
Describe your patchwork of tools and your processes. I’ll tell you frankly whether custom is justified, what it would cost, and whether an off-the-shelf tool would do the job better. No commitment.
Last updated: 11 June 2026 · Author: Rémy Ardurat, Product Builder · Price ranges indicative of the French market, to be refined during scoping depending on your project. Page published by buildwithremy.com.