Open Source vs Commercial SIEM: Which Fits You

Every security team asks this question eventually: do we pay for a commercial SIEM, or do we stand up something open source and keep the licensing budget for headcount instead? The honest answer is that “open source SIEM” and “commercial SIEM” aren’t really competing on the same axis — one trades license cost for operational labor, and the other trades operational labor for license cost. Neither is free in absolute terms.

Here’s how the two options actually compare, so you can budget for the real cost rather than the sticker price.

Open Source SIEM Options (Wazuh, Elastic)

Wazuh is a fully open source, unified XDR and SIEM platform released under the GPLv2 license. There’s no license fee, no per-agent charge, and no feature paywall gating off detection rules, compliance mapping, or threat hunting — the entire product is in the free binary. If you want someone else to run the infrastructure, Wazuh also sells a managed cloud tier (roughly $571/month for a small 100-agent deployment, scaling to $1,467/month for 500 agents), but that’s optional, not a requirement to use the platform.

Elastic Security sits in a middle zone. Elastic publishes a Basic subscription that is free indefinitely and includes core SIEM functionality — log ingestion, Kibana dashboards, pre-built detection rules, and the Security app UI. Beyond that, Elastic layers paid tiers (Standard, Gold, Platinum, Enterprise) that add machine learning, cross-cluster search, endpoint security, and SOAR, priced against provisioned compute and storage rather than headcount or data volume. So “Elastic” can mean a genuinely free deployment or a fairly expensive one, depending on which capabilities you need.

The pattern across both: the software license cost approaches zero, but you’re taking on the work a commercial vendor would otherwise do for you — index management, rule tuning, upgrade testing, and incident triage tooling.

Commercial SIEM Options (Splunk, QRadar, and Others)

Splunk prices primarily on ingest volume. List pricing for the core platform runs roughly $1,800-$2,500 per GB/day on a 1-year term, and the Enterprise Security add-on layers another $400-$600/GB/day on top. Splunk also offers workload-based pricing (tied to compute consumed by searches and dashboards) as an alternative to raw ingest pricing, which can help if your workload is search-heavy rather than volume-heavy. Enterprise Security’s correlation searches, risk scoring, and threat intel indexing commonly inflate effective ingestion by 50-100% over what you’d expect from raw log volume alone, which is the line item that catches budgets off guard.

IBM QRadar licenses primarily by Events Per Second (EPS) and Flows Per Minute (FPM), or by Managed Virtual Servers (MVS) under the Enterprise model. Quotes are custom, typically landing between $15,000 and $250,000+ per year depending on deployment size, and implementation costs frequently match or exceed the first year’s license fee. Maintenance contracts add another 20-25% annually for on-premises deployments (cloud subscriptions roll this in), though negotiated discounts of 25-35% are routine on multi-year commitments above 5,000 EPS.

What you’re buying with either vendor: a support contract, a product roadmap someone else maintains, a large hireable talent pool who already know the tool, and (for QRadar and Splunk Enterprise Security specifically) built-in correlation and case management that would otherwise be a build-it-yourself project on open source.

Total Cost of Ownership Compared (License vs Ops Overhead)

The break-even point isn’t about company size so much as whether you already have (or are willing to hire) the engineering capacity to run open source SIEM well. A team that’s going to hire a dedicated detection engineer anyway may find open source SIEM cheaper in total. A team that would rather buy that expertise as a subscription will often find a commercial platform cheaper than building the equivalent in-house capability from scratch.

Support and Scaling Limits Compared

Commercial SIEM support is bounded and contractual: you file a ticket, you have an SLA, and the vendor’s roadmap determines what gets built next. Open source SIEM support is either community-based (forums, GitHub issues, documentation) or a paid layer on top of the free core (Wazuh Cloud, Elastic’s paid tiers) — you can buy your way to something support-contract-shaped, but it’s opt-in rather than bundled.

Scaling looks different too. Splunk and QRadar both have well-documented enterprise deployment patterns for very large environments — the vendors have done this hundreds of times and the failure modes are known. Open source SIEM scales technically (Wazuh and Elastic both run at large scale in production), but the scaling work — cluster sizing, index lifecycle management, query performance tuning — falls on your team rather than a vendor’s professional services organization. At genuinely large scale, the “free” license cost can be offset by the additional headcount needed to keep the cluster healthy.

Which Fits Your Team’s Size and In-House Expertise

Choose open source SIEM (Wazuh, Elastic Basic) if: you already have security engineers comfortable operating Linux infrastructure and tuning detection rules, your log volume is moderate and predictable, and the licensing budget you’d save is worth more to you than a vendor support contract.

Choose commercial SIEM (Splunk, QRadar) if: you need a support contract with an SLA, your team is small relative to your log volume and can’t absorb the operational overhead of running SIEM infrastructure, or you need built-in correlation, case management, and compliance reporting that would otherwise be a multi-quarter build project on top of open source tooling.

A hybrid approach is common in practice: some teams run Wazuh or Elastic for high-volume, lower-priority log sources (to avoid paying commercial ingest pricing on noisy data) while keeping a commercial SIEM for the smaller set of high-fidelity, high-priority detections where vendor-maintained correlation logic and support matter most.

Sources

• Wazuh - Open Source XDR. Open Source SIEM. (GPLv2 license, no license fee or feature paywall on the core platform; managed cloud pricing from $571/mo for 100 agents)
• Splunk - Ingest Pricing (ingest-based licensing model for the core platform)
• Splunk - Pricing (workload pricing as an alternative to ingest-based pricing)
• Elastic Security for SIEM - Price Estimator (Standard/Gold/Platinum/Enterprise tiers; free Basic tier with core SIEM functionality)
• IBM Security QRadar SIEM - Pricing (EPS/FPM and Managed Virtual Servers licensing models)

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