Here's a number that should bother you: license fees are rarely more than 40% of what a SIEM actually costs you. The other 60% shows up later, spread across storage bills, tuning hours, and the analyst you hired six months ago who still can't get through the alert queue.
Most vendor conversations never get past that first 40%. That's the number on the quote. That's what gets compared in the RFP. And it's the number that makes "renting" a SIEM look cheap right up until the year-two invoice lands.
I want to walk through what SIEM ownership actually costs in 2026, where the number quietly grows every year whether you touch the platform or not, and when it actually makes sense to stop renting and build your own. Not as a sales pitch. As a framework you can run against your own ingestion numbers this afternoon.
Quick Verdict
Keep renting if: your ingestion is under roughly 50 GB/day, you don't have in-house platform engineers, or your compliance needs are standard and well-served by an off-the-shelf product.
Consider building if: you're pushing past 100 GB/day, you're paying for a multi-tenant setup across several business units or clients, or a chunk of your annual spend goes toward per-GB fees for log types a vendor's licensing model wasn't built to handle cheaply — think NDR telemetry, identity logs, or cloud audit trails.
Now let's get into why.
What "Renting" Actually Costs
Vendors price SIEM three different ways, and it matters which one you're signed up for.
Splunk charges by ingestion volume, and depending on your deployment model and region, that lands anywhere from roughly $80,000 a year for a 100 GB/day base platform on AWS Marketplace up to $300,000+ once you add the Enterprise Security module, which typically runs 1.5 to 2x the base platform cost (Security Boulevard).
Microsoft Sentinel is more transparent about its per-GB rate — $4.30/GB in East US, $5.59/GB in West US — but transparency doesn't mean cheap. At 100 GB/day on the analytics tier, you're looking at $156,950 to $204,035 a year, before you've added a single custom detection rule.
IBM QRadar skips per-GB pricing entirely and charges by Events Per Second: about $12,074 a year for every 500 EPS unit. That model punishes you differently — a noisy identity provider or a chatty firewall can blow your EPS budget without moving your GB/day number at all.
Elastic sits at the cheap end, $0.55 to $1.10/GB, which explains why so many teams that eventually build their own platform start from an Elastic or OpenSearch base rather than from zero.
Here's the part that actually stings, though: telemetry volume grows 20 to 30% a year in a typical enterprise, driven by identity monitoring, endpoint sprawl, and cloud workloads that didn't exist three years ago (Cribl). You don't renegotiate that growth. It just shows up on next year's bill, on a pricing model you didn't choose, for data you may not even be querying.
The Other 60%
License fees get all the attention because they're the line item a CFO can see. The rest of the cost is quieter and, frankly, harder to budget for.
Security Boulevard's 2026 breakdown puts it at roughly: licensing 40%, staffing 22%, storage 14%, integration 10%, tuning 9%, threat intelligence feeds 7%. Add those up and you get something close to the real number — and staffing alone is more than half of what licensing costs.
That staffing line isn't abstract. It's the analyst tuning correlation rules so a new SaaS integration doesn't trigger 400 false positives a day. It's the engineer who spends a quarter migrating parsers because the vendor changed a schema. None of that shows up in the sales deck. All of it shows up in your headcount plan.
And retention is its own trap. Compliance regimes increasingly want 12, 18, sometimes 24 months of searchable logs — not just cold storage, searchable. Hot and warm storage tiers cost real money, and most per-GB quotes only cover the cheapest tier by default.
What "Building" Actually Means
Building your own platform doesn't mean writing a SIEM from scratch — nobody sane does that. It means standing up a stack on open-source foundations (Elasticsearch, OpenSearch, or Wazuh are the usual choices), engineering the ingestion pipeline, detection logic, and SOAR playbooks around your environment, and owning the result outright instead of licensing it forever.
The economics flip once you clear a certain ingestion threshold. Instead of paying per gigabyte forever, you pay once to build the platform, then carry infrastructure and a smaller ongoing engineering cost — no scaling tax every time your log volume grows.
WhyCrew, an engineering firm that builds custom SIEM and SOAR platforms for MSSPs and regulated operators, publishes actual numbers from these engagements: a typical build runs €60,000 to €250,000 depending on tenant count and ingestion volume (enterprise deployments with heavier compliance requirements can reach €400,000), with most clients seeing a 40–70% reduction in SIEM cost of ownership within the first year and breakeven somewhere between 12 and 18 months. They also claim zero-downtime cutovers off Splunk, Sentinel, and QRadar — running the new platform in parallel until detection parity is verified before switching over, which matters a lot if you're the person who has to explain a coverage gap to an auditor.
I'm citing that as one real data point, not a recommendation — do your own vendor diligence. But it's a useful anchor for what the "build" side of this framework actually costs in practice, and it lines up with the ranges independent pricing research shows for a mid-size to large enterprise deployment.
There's a second effect worth mentioning if you're an MSSP: once you own the platform, multi-tenant isolation and white-labeling become an engineering decision, not a licensing negotiation. You're not paying a per-tenant markup to a vendor for something you could build once and reuse across every client.
The Framework
Run these four questions against your own environment before you decide anything.
- What's your ingestion volume, honestly? Under 50 GB/day, the math almost never favors building. You won't hit breakeven before your team burns out maintaining a platform that a vendor would've handled for less than the engineering cost alone.
- Is your cost growing faster than your headcount? If your SIEM bill is climbing 20-30% a year (normal, per the telemetry growth data above) and your security budget isn't climbing at the same rate, that gap compounds. Three years of that gap usually covers most of a custom build.
- Do you actually need multi-tenancy or white-labeling? MSSPs and holding companies running SIEM across multiple business units pay a real premium for vendor multi-tenant licensing. That premium is often the single biggest argument for owning the platform outright.
- Can you staff it? This is the one people skip. Owning a platform means owning its maintenance. If you can't hire or retain two or three engineers who understand your detection stack, renting — even at a worse per-GB rate — is still the safer bet. A platform nobody can maintain is worse than an expensive one that works.
Where Building Goes Wrong
I'd be doing you a disservice if I left this at "build and save money," because it isn't that simple.
Teams that build without the engineering depth to support it end up with a platform that quietly rots: detection rules nobody updates, a data pipeline that breaks every time a new log source gets added, and an "owned" SIEM that's actually more expensive than the vendor product it replaced once you count the engineer-hours nobody logged.
The honest version of this framework is: building only pays off if you commit to maintaining it like a product, not a project. If your team treats the migration as a one-time initiative and moves on, you've traded a predictable vendor bill for an unpredictable maintenance debt. That's a worse trade, not a better one.
Do the Math on Your Own Numbers
Pull your last 12 months of SIEM invoices. Add up licensing, storage overage, and the hours your team spent on tuning and integration work that never showed up as a line item. Compare that real number — not the sticker price — against what a three-year build-and-own plan would cost at your actual ingestion volume.
For most teams under 50 GB/day, renting still wins. Past that, especially if you're carrying multi-tenant or heavy compliance overhead, the framework above should tell you which side of the line you're on — and what it would actually take to move.
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