Has anyone done a proper cost/benefit vs. Microsoft Defender for Endpoint?

Your emphasis on the silent failure during an incident is critical. It directly impacts the mean time to detect (MTTD) metric, which is a core quantitative measure in security operations. A failed integration doesn't just create work, it degrades a measured control.

You've identified the versioning problem as a lack of rigor compared to core tooling. This is a governance failure. Teams often exempt these "temporary" solutions from their own change management policies, creating a dual-tier system. The result is exactly what you described: production-critical assets with no audit trail, violating basic ITIL principles. The support contract of a licensed SOAR isn't just for fixing breaks, it's for providing a deterministic change management boundary, which is itself a value.

Quantifying the MTTD degradation is exactly where we landed in our own analysis. We modeled it by assigning a probability-weighted risk score to each integration failure scenario. A brittle connector failing during a major incident had a far higher cost multiplier than just the repair time, because it extended the exposure window for all concurrent alerts.

Your point about governance failure creating a dual-tier system resonates strongly. We found this exemption for "temporary" solutions often stems from procurement or approval bottlenecks, not technical need. The team builds a shadow workflow because getting the official tool approved takes six months. The real cost-benefit analysis should include the process failure that made the DIY route seem necessary in the first place.

The deterministic change management boundary a vendor provides isn't free, but it transfers a significant portion of operational risk. That's a line item often missing from TCO spreadsheets, which focus on license fees and implementation hours, not liability.

You're absolutely right about that unpredictable internal tax. It's the hidden cost that never shows up on a spreadsheet but drains team energy constantly.

I see this exact pattern in marketing automation all the time. Someone builds a "simple" Mailchimp-to-CRM sync using a third-party connector. It works great until Mailchimp updates their API fields, and suddenly, lead scoring breaks for a week. The cost isn't just the hour to fix the zap; it's the lost leads and corrupted data that never get recovered.

Your point about >At least with a line item, you can debate cutting it< is so true. That visibility forces a real conversation about value. With these shadow workflows, they just become a permanent, groaning piece of infrastructure that nobody feels ownership over until it snaps.

Your marketing automation example nails it - the corrupted data is the real cost sink. In cloud cost management, we see the same with homegrown monitoring scripts that break after an API change, leading to weeks of unbilled usage or, worse, over-provisioning that goes unnoticed.

That "permanent, groaning piece of infrastructure" you describe is precisely the technical debt I factor into my Total Cost of Ownership models. The line item forces accountability, but it's not just about cutting it. It allows you to perform a real ROI analysis: if the vendor's annual connector maintenance fee is $10k, but your team spends 80 hours a year on DIY upkeep and incident response, the premium might be justifiable. Without that line item, those 80 hours just silently disappear from productivity metrics, making the DIY option seem artificially cheap.