The verdict in three sentences
For a practice under 15 staff, a vendor SaaS tool (EUR 25 to 60/user/month) stays the rational choice: fast rollout, maintenance included, zero technical debt. Beyond 25 to 30 staff, or when your accounting production demands unusual workflows, a custom tool (EUR 40,000 to 90,000) pays off over 4 to 5 years. The real variable is not the sticker price but the 5-year total cost of ownership (TCO) and the administrative hours you claw back.
Vendor vs custom: what you actually pay for
A practice-management tool covers four core functions: time and engagement tracking, document management (DMS), fee billing, and profitability steering. Vendors charge per user; custom is paid as a project, then annual maintenance (8 to 12 % of the build).
| Criterion | Vendor SaaS | Custom |
|---|---|---|
| Entry cost | EUR 0 to 3,000 (setup) | EUR 40,000 to 90,000 |
| Recurring price | EUR 25 to 60/user/month | Maintenance 8-12 %/year |
| Time to launch | 2 to 6 weeks | 14 to 24 weeks |
| Workflow customization | Limited to options | Total |
| Accounting production integration | Standard connectors | Dedicated custom API |
| Vendor lock-in | High (price hikes) | Low (you own the code) |
5-year TCO: the calculation that decides
The classic trap is comparing a monthly subscription to a one-off investment. Spread over 5 years, the gap narrows fast as the practice grows.
| Headcount | Vendor (EUR 45/user/month) over 5 years | Custom (EUR 65,000 + 10 %/year) over 5 years |
|---|---|---|
| 8 staff | EUR 21,600 | EUR 97,500 |
| 15 staff | EUR 40,500 | EUR 97,500 |
| 25 staff | EUR 67,500 | EUR 97,500 |
| 40 staff | EUR 108,000 | EUR 97,500 |
| 60 staff | EUR 162,000 | EUR 97,500 |
The tipping point sits around 30 to 35 staff: below it, the vendor wins; above it, custom becomes cheaper AND better fitted.
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Mini case study
Claire, partner at a 22-staff accounting practice in Nantes. Her teams lose on average 45 minutes per person per day re-keying data between the time tool, production and billing. Across 22 people and 210 working days, that is roughly 3,465 hours/year. At a loaded hourly cost of EUR 38, the annual loss reaches EUR 131,670. A custom tool at EUR 70,000 that removes 70 % of that re-keying frees nearly EUR 92,000/year: it is paid back in under 10 months, before counting quality gains and calm during tax season.
FAQ
Should we go custom from day one of the practice? Rarely. As long as your processes aren't stabilized, a vendor at EUR 25-45/user/month keeps you flexible without locking up EUR 60,000.
What maintenance budget for a custom build? Budget 8 to 12 % of build cost per year, i.e. EUR 5,600 to 10,800/year for a EUR 70,000 project. It covers fixes, regulatory updates and hosting.
Can the tool connect to my existing accounting production? Yes, via API or connectors. With a vendor, check the native integration list; with custom, the connection is built specifically, ensuring a re-keying-free flow.
How long to deploy a custom tool? Expect 14 to 24 weeks depending on scope, including framing, development, data migration and team training.
Does GDPR complicate hosting client data? EU hosting and encryption are standard. A custom project lets you control data location and retention policy, a sensitive point for a practice.
Let's scope your project. Tell us your headcount, your current production tools and your target budget, and we'll tell you frankly whether vendor or custom is the right math. 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.
