The verdict in three sentences
An application security audit (pentest) costs 4,000 to 15,000 EUR in Amsterdam in 2026, depending on app size and test depth. Add 3,000 to 12,000 EUR of remediation and a re-test to validate fixes. Against the average cost of an incident (GDPR breach, ransom, downtime), an annual audit is the cheapest insurance you can buy.
Cost by audit type
Not all pentests are equal: a black-box test is fast, a white-box test with code review is deeper and pricier. 2026 order of magnitude:
| Audit type | Scope | Timeline | Indicative cost |
|---|---|---|---|
| Black box (external) | Public app | 3 - 5 days | 4,000 - 7,000 EUR |
| Grey box (test account) | App + roles | 5 - 8 days | 7,000 - 11,000 EUR |
| White box (+ code) | App + code + infra | 8 - 15 days | 11,000 - 18,000 EUR |
| Dedicated API audit | REST endpoints | 3 - 6 days | 4,500 - 9,000 EUR |
| Post-fix re-test | Targeted check | 1 - 2 days | 1,500 - 3,000 EUR |
The audit covers the OWASP Top 10 (injection, broken access control, misconfiguration, XSS, SSRF...), with a report prioritised by severity (critical / high / medium / low) and proof of exploitation.
Audit cost versus incident cost
The real calculation is not the pentest price but the avoided risk. 2026 order of magnitude for an SME:
| Scenario | Estimated impact | Likelihood without audit |
|---|---|---|
| Customer data breach (GDPR) | 20,000 - 150,000 EUR | Medium to high |
| Ransomware (downtime + ransom) | 30,000 - 250,000 EUR | Medium |
| Defacement / brand damage | 5,000 - 40,000 EUR | Low to medium |
| Fraud via payment flaw | 10,000 - 100,000 EUR | Medium |
| GDPR fine | up to 4 % of revenue | Variable |
A 6,000 EUR pentest that prevents even one 50,000 EUR incident shows a 1-to-8 ratio. Recommended frequency is annual, plus a test on every major change or before a sensitive release.
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Mini case study
The CISO of an Amsterdam fintech (payment management app) must harden before going live. Scope: grey-box audit + dedicated API audit. Quote: grey-box pentest 9,000 EUR + API audit 6,000 EUR + re-test 2,500 EUR = 17,500 EUR, estimated remediation 8,000 EUR. The audit reveals broken access control letting one account reach other accounts' payments: a flaw that, if exploited, would have cost over 120,000 EUR in fraud and fines. Immediate payback.
FAQ
How long does a pentest take? Between 2 and 4 weeks total: 1 week of scoping and access, 3 to 8 days of testing, then the report. The re-test follows your fixes, within 1 to 2 days.
Scan versus pentest? A scan (a few hundred euros) finds known flaws; a pentest (4,000 to 15,000 EUR) adds manual exploitation and business logic. The two are complementary.
Is remediation included? Usually not. Plan for 3,000 to 12,000 EUR depending on the number and severity of flaws. Some auditors offer a bundle: audit + remediation + re-test.
How often should we audit? At least once a year, and always before a sensitive release or after a major redesign. Client requirements (large accounts, banks) often mandate an annual cadence.
Is an audit needed for GDPR compliance? GDPR requires "appropriate technical measures". A documented pentest is strong evidence of diligence and can sharply reduce the fine risk (up to 4 % of revenue).
Let's scope your project. Tell us the app type, the scope (web, API, mobile), the audit level you want and your indicative budget. 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.
