Compare / Splunk vs Sentinel

Splunk vs Microsoft Sentinel cost: 2026 side-by-side at 5, 50, and 200 GB

Head-to-head cost comparison. Per-GB Splunk versus commitment-tier Sentinel at five log volume bands, five-year TCO model, and where each vendor genuinely wins. Splunk baseline and Sentinel rates re-verified against 2026 pricing. Updated October 2026.

Page updated 13 October 2026/First published 15 May 2026

Splunk Cloud

$1,265/GB base

At 50 GB, filed list; ~2x with ES

Sentinel

$4.30/GB

PAYG; $2.96 at 100 GB commit

50 GB/day

Sentinel wins

$59K-$78K vs ~$124K

5-year TCO

$337K vs $565K

50 GB/day, with renewals

The pricing models in collision

Splunk and Sentinel both price per gigabyte ingested, which makes the comparison superficially simple and structurally misleading. The first complication is that Splunk Cloud's base ingest is genuinely competitive (about $63K at 50 GB per day, $1,265 per GB/day per year at list). The second complication is that Splunk requires Enterprise Security as a separate licence (adding about 96% at 50 GB/day, about $61K, and 55-75% above that) for full SIEM functionality, while Sentinel includes equivalent capability in the base licence. The third complication is that Sentinel ingests Microsoft 365 audit logs at no additional charge, which materially advantages Sentinel in any Microsoft-heavy environment.

At 50 GB per day, Splunk Cloud lists at about $63K base ingest plus about $61K for Enterprise Security, about $124K before any EA discount. Sentinel at 50 GB per day with 30 percent Microsoft 365 share pays for about 35 billable GB at the $4.30 PAYG rate, roughly $55K per year, or about $59K on the promotional commitment tier. The gap at this profile is roughly 2.1x to 2.3x in Sentinel's favour at list. Splunk's base ingest is competitive; its premium over Sentinel is driven by the separate Enterprise Security licence and by Sentinel's free Microsoft 365 ingest, not by an expensive base rate.

The two converge at very high log volumes. By 1,000 GB per day, Splunk's filed 2026 list pricing and negotiated multi-year EA discounts (35-40 percent off list) land close to Sentinel's larger commitment tiers, where Sentinel's effective rate compresses similarly (falling to about $2.05 per GB at the 50,000 GB per day tier). At very large enterprise scale, the two frequently land within a narrow band on licence-only terms, with the buying decision turning on factors other than raw cost (detection content depth, SOC familiarity, broader Microsoft consolidation strategy, on-premise data residency).

Same environment, both vendors

Volume	Splunk Cloud + ES	Sentinel commit tier	Winner	Note
5 GB/day	~$10K (base only)	$8K	Sentinel	ES is not sold below 50 GB/day; Sentinel free MS365 ingest dominates at small scale
50 GB/day	~$124K	$59K-$78K	Sentinel	Gap is the ES premium plus MS365 free ingest, not base ingest (~$63K)
200 GB/day	~$312K	$200K	Sentinel	Splunk base (~$195K) competitive; ES drives the premium
500 GB/day	~$667K	$462K	Sentinel	Splunk EA discounts narrow it
1,000 GB/day	~$1.29M	$905K	Sentinel at list	A 35-40% Splunk EA discount (~$774K-$839K) reaches Sentinel parity

Annual licence figures (Sentinel East US simplified rates, verified August 2026). Splunk rows are Splunk Cloud plus Enterprise Security at filed list, before any discount; ES is not sold below 50 GB/day, so the 5 GB/day row is base only. Splunk publishes no per-GB price on splunk.com; its end-customer list prices are public through its UK G-Cloud 15 filing and the AWS Marketplace Splunk Enterprise listing. Multi-year EA discounts on Splunk are how parity arises at very high volume. All figures are before Sentinel's free Microsoft 365 ingest, which typically removes a further 25-35 percent of billable volume.

Five-year TCO at 50 GB per day

Year	Splunk Cloud + ES	Microsoft Sentinel
Year 1 (50 GB/day)	$124K (with ES, no discount)	$78K (PAYG, no discount)
Year 2	$109K (TCO reduction)	$64K (commitment tier)
Year 3	$105K (steady state)	$62K (steady state)
Year 4	$111K (5% inflation, renewal)	$65K (5% inflation, renewal)
Year 5	$116K	$68K
5-year total	$565K	$337K

Five-year cumulative includes initial licence, year-over-year renewal inflation (5% assumed), and standard Year 2 TCO compression as integration costs roll off. Excludes one-time migration costs.

When Splunk genuinely wins

+Mature SOCs with deep custom Splunk ES content and detection libraries built over years; the migration cost outweighs the licence saving
+Organisations whose log volume sits above 1,000 GB per day and whose multi-year EA negotiation produces 35-40 percent off list
+Detection content depth where Splunk ES, premium content packs, and the SOAR add-on combine to deliver investigation depth Sentinel cannot match
+On-premise data residency requirements where Splunk Enterprise self-managed is a cleaner answer than Azure Government Sentinel
+Existing Splunk muscle memory: organisations whose security analysts trained on Splunk see productivity tax in cross-platform retraining that licence saving cannot recover

When Sentinel genuinely wins

+Microsoft 365 and Azure-heavy environments where free Microsoft ingest is the dominant log source and structurally tilts the comparison
+Mid-market organisations under 200 GB per day where commitment tier pricing produces 35-50 percent below Splunk Cloud with Enterprise Security at list
+Organisations consolidating onto Microsoft Defender, Defender for Endpoint, and Defender for Cloud, where Sentinel bundling compounds across the security stack
+Cloud-native deployments where the operational simplicity of Azure-native SIEM matters more than detection content depth
+Customers exiting Splunk after multi-year per-GB bill explosions, where the migration cost amortises across 24-36 months of reduced spend

FAQ

Common questions

Is Splunk or Sentinel cheaper for a 50 GB-per-day environment?

Sentinel is cheaper at 50 GB per day. Pay-as-you-go at $4.30 per GB lands at roughly $78K per year for the licence, and the promotional 50 GB commitment tier (public preview, sign up by 31 December 2026) cuts that to about $59K. Splunk Cloud at 50 GB per day lists at about $63K base ingest plus about $61K for Enterprise Security, about $124K before discount. With aggressive Splunk EA negotiation (25-30 percent off), Splunk lands around $87K to $93K. So the gap is roughly 1.6x to 2.1x at list, and still about 1.5x to 1.6x against the commitment tier after an aggressive EA discount. Sentinel's edge comes mainly from free Microsoft 365 ingest and from bundling SIEM capability that Splunk charges for separately through Enterprise Security.

Does Splunk justify its premium over Sentinel?

For mature SOCs with deep custom Splunk ES content built over years, the migration cost frequently outweighs the licence saving for 24-36 months. Splunk Enterprise Security delivers genuinely superior search performance, a deeper content library (premium content packs, ITSI integration, broader community apps), and an investigation workflow that Sentinel does not yet match. For organisations where these capabilities are the binding constraint, Splunk justifies the premium. For organisations whose detection content is broadly portable (SIGMA rules, MITRE ATT&CK aligned content) and whose SOC is willing to retrain, Sentinel's cost advantage at mid-market scale is decisive.

How does Microsoft 365 ingest factor into the Sentinel comparison?

Microsoft Sentinel ingests Microsoft 365 audit logs, Azure AD sign-in logs, and Microsoft Defender alerts at no additional charge above the Sentinel licence itself. For organisations where Microsoft sources comprise 30-60 percent of total log volume (common in Microsoft-heavy enterprises), the structural Sentinel cost advantage compounds dramatically. Splunk ingests the same Microsoft sources at full per-GB rate. A 50 GB-per-day environment where 25 GB is Microsoft 365 audit logs effectively pays Splunk for 50 GB and Sentinel for 25 GB, halving the commercial comparison further in Sentinel's favour.

What about Splunk Cloud versus Splunk Enterprise on-premise in this comparison?

Splunk Enterprise self-managed wins on per-GB licence cost above approximately 750 GB per day, where amortised hardware beats Splunk Cloud subscription. Below that volume, Splunk Cloud is the practical default. The Sentinel comparison flips slightly: Splunk Enterprise on-premise at 1,000 GB per day with full multi-year EA discount can land within 15-20 percent of Sentinel, where Splunk Cloud at the same volume lists at about $1.29M with Enterprise Security (about 1.4x Sentinel's $905K) and closes that gap only on EA-discounted terms. For very large enterprises evaluating SIEM modernisation, the choice is genuinely Splunk Enterprise versus Sentinel rather than Splunk Cloud versus Sentinel.

What is the migration cost from Splunk to Sentinel?

Migration cost varies materially with detection content depth and analyst retraining requirements. A typical mid-market migration (50 GB per day, 200 detections, 10-person SOC) runs $150K-$300K in professional services plus 4-8 months calendar time. Migration of legacy Splunk ES correlation searches to Sentinel KQL queries is the largest single workstream. For organisations where the licence saving is $50K-$100K per year, the payback is 2-4 years, which is rarely the right investment unless the organisation is also consolidating onto Microsoft 365 and Microsoft Defender for broader strategic reasons. For organisations where the licence saving is $300K-plus per year, the payback is under 12 months and the migration is straightforwardly the right call.