The short answer
| Scope | Published range |
|---|---|
| First phase for a B2B company of 30–80 employees (4–6 departments, replacing 2–3 critical pieces) | €40,000–120,000 |
| Initial build of a custom system that replaces a generic ERP | €80,000–180,000 |
| Keeping the system alive (improvements, supervised AI agents, monitoring) | €5,000–15,000 a month |
| First module live and connected to real operations | 8–14 weeks from signing |
For small businesses, Spanish agencies publish ranges of €5,000 to €60,000 with €200–800 a month of maintenance. That is the Spanish market, not our range: we build for companies of 20 to 500 employees.
What moves the price
- How many systems have to talk to each other. Every integration with an existing ERP, CRM, carrier or machine adds work and risk.
- How many exceptions there are. A process that works "except when…" costs more than one that doesn't, and the exceptions are rarely written down.
- Data migration. Moving data out of a closed system is one of the most expensive parts of any change.
- Regulation. In pharma or finance, validation and traceability add documented work on top of the build.
- How much AI decides. An agent that decides with your margins needs supervision, and that is a running cost.
The comparison most buyers skip: five years of licences
A SaaS for 50 users at €80 a month for 60 months is €240,000 in licences alone. Add the implementation of a mid-market SaaS (€15,000–80,000), a partner hours package (€800–1,500 a month) and integrations (€200–800 a month). A generic ERP costs €150–200 per user per month in licences, and getting your data out when you change ERP can cost €100,000–500,000 in consulting. Custom software implementation, by comparison, runs €40,000–120,000, and there is no per-user licence afterwards.
That doesn't make custom software the right answer for everyone. If your processes are standard and your team is small, a well-implemented off-the-shelf product is cheaper and faster. The sum has to be done with licences, migrations and partner hours included.
Why we don't quote before looking
Because it would be lying to you. The price depends on what we find: how the work really moves, which exceptions exist, what data you have and what state it's in. The analysis comes first, under NDA, and ends in a report with the changes prioritised by impact on your P&L. The quote comes after that. More on how we build in custom software and, for a system that replaces your ERP, custom ERP.
How we start
Always the same way. Day zero: an NDA signed before you show us anything. Then the Nexus team analyses your operation and delivers a report with the exact changes, prioritised by impact on your P&L. Then you decide. Nexus Elite AI is an engineering boutique in Barcelona: two people, no juniors, no subcontractors, and never more than seven clients at a time. Apply and we reply within 24 business hours; if there is no fit, we tell you in writing.
Frequently asked questions
How much does custom software cost for a mid-sized company?
For a B2B company of 30–80 employees replacing two or three critical pieces of its stack, a reasonable first phase costs between €40,000 and €120,000. Replacing a generic ERP entirely runs €80,000–180,000 for the initial build.
What are the running costs after launch?
Keeping the system alive — improvements, supervised AI agents, functional evolution and monitoring — runs between €5,000 and €15,000 a month depending on complexity. There are no per-user licences.
Is custom software cheaper than SaaS?
Sometimes, over five years. A SaaS for 50 users at €80 a month is €240,000 in licences over 60 months, before implementation, partner hours and integrations. If your processes are standard and your team small, SaaS is usually the better choice.
How long does it take?
The first module is live and connected to real operations 8 to 14 weeks after signing. The full system is built module by module, starting with the one that costs you the most margin.