The verdict in three sentences
For an M&A advisory firm opening fewer than 6 data rooms a year, an off-the-shelf VDR remains the most rational choice. Above 8 to 10 deals a year, a custom data room at EUR 40,000 to 80,000, hosted and encrypted in a controlled jurisdiction, pays for itself in 12 to 24 months and strengthens the firm's image with sellers. The figures below come from the Paris market and give New York firms a solid benchmark once converted to USD: the decision hinges on deal volume, buyers' security requirements and the ability to maintain the tool over time.
What a sell-side data room must do in 2026
Buyers, funds and their advisers expect a standardised feature set. A custom data room must at least match market VDRs on the following points.
| Feature | Minimum requirement | Indicative development cost |
|---|---|---|
| Numbered index tree and bulk upload | Drag and drop of 2,000 to 10,000 documents | EUR 4,000 to 8,000 |
| Permissions by buyer group and folder | View only, print, download | EUR 5,000 to 10,000 |
| Dynamic watermark (name, email, date, IP) | Applied to every page viewed or downloaded | EUR 3,000 to 6,000 |
| Access log and activity reports | Who saw what, for how long, export for the seller | EUR 4,000 to 8,000 |
| Q&A by document batch | Buyer, adviser, seller workflow with approval | EUR 6,000 to 12,000 |
| Strong authentication and access expiry | Two-factor, access cut at end of process | EUR 3,000 to 6,000 |
| Encryption at rest and in transit, end-to-end option | Keys managed in-jurisdiction, final encrypted archive handed to client | EUR 5,000 to 15,000 |
End-to-end encryption deserves an informed decision: it protects even against the hosting administrator, but complicates full-text search and previews. Many firms choose encryption at rest with keys managed by a local host, and reserve end-to-end for the most sensitive files.
Off-the-shelf VDR or custom data room: the break-even point
Market VDRs charge per deal, per page or per month open, often EUR 2,000 to 10,000 per deal for a mid-market sale of EUR 5 to 50 million. The table below compares annual cost assuming an average of EUR 5,000 per deal against a EUR 60,000 custom data room amortised over three years, plus EUR 12,000 per year of encrypted hosting and maintenance.
| Deals per year | Market VDR cost (EUR 5,000 per deal) | Annual custom cost (amortisation and operations) | Annual difference |
|---|---|---|---|
| 4 | EUR 20,000 | EUR 32,000 | -EUR 12,000 |
| 6 | EUR 30,000 | EUR 32,000 | -EUR 2,000 |
| 8 | EUR 40,000 | EUR 32,000 | +EUR 8,000 |
| 10 | EUR 50,000 | EUR 32,000 | +EUR 18,000 |
| 15 | EUR 75,000 | EUR 32,000 | +EUR 43,000 |
| 20 | EUR 100,000 | EUR 32,000 | +EUR 68,000 |
Break-even sits around 6 to 7 deals per year. It drops if your deals are document-heavy (per-page billing) and rises if you negotiate an unlimited annual plan with a vendor, often offered between EUR 25,000 and 45,000 per year.
Hosting, compliance and liability
A sell-side data room holds employee personal data, client contracts and non-public financial information. Hosting with an ISO 27001 certified provider, ideally on a SecNumCloud qualified offer for sensitive French files (or SOC 2 Type II in the US), reassures sellers and buyers. Count EUR 300 to 900 per month for encrypted infrastructure with backups on a second site.
Also plan an annual penetration test by a specialist firm, around EUR 5,000 to 10,000, and a handover procedure: at closing, an encrypted archive on media handed to the seller, then certified data purge. These items now appear in private equity security questionnaires.
Mini case study
Antoine, partner at a Paris firm advising on SME sales, opens 15 data rooms a year for deals of EUR 8 to 40 million. His current VDR budget reaches EUR 72,000 per year, i.e. EUR 4,800 per deal on average.
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
Custom project: EUR 65,000 of development with watermarks, access logs, Q&A and encryption at rest, then EUR 14,000 per year of hosting, maintenance and penetration testing. Over three years, total cost reaches 65,000 plus 42,000, i.e. EUR 107,000, against EUR 216,000 of VDR fees.
Calculation: three-year savings come to EUR 109,000, and the project pays back in about 13 months (65,000 divided by monthly savings of EUR 4,830). The firm also gains a branded interface, shown to sellers from the mandate stage.
FAQ
Is a custom data room as secure as a market VDR?
It can be if the architecture follows the same standards: AES-256 encryption, strong authentication, full logging and an annual penetration test. Security often accounts for 20 to 25% of the development budget.
How long does it take to build a custom data room?
Count 10 to 16 weeks for a complete first version, penetration test included. Run a pilot deal on a mid-sized file before rolling it out.
Do buyers accept a data room built by the advisory firm?
Yes, if they find the expected features: index, watermark, Q&A, log export. Prepare a 2 to 3 page security sheet to send to buyers' advisers.
Can the platform be reused for other purposes?
Yes, many firms also use it for fundraising and client document sharing outside sale processes. These uses further reduce the cost per file.
Do we need end-to-end encryption?
Only for the most sensitive files. It adds EUR 5,000 to 15,000 to the budget and limits full-text search, which slows buyers down.
Let's scope your project. Tell us your annual deal count, security requirements and current VDR budget: we will cost the scope, encrypted hosting and timeline of your data room. 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.
