The Hidden Cost of Microsoft 365 Storage: What’s Lurking in Your 1 TB Pool

Every Microsoft 365 tenant comes with the same starting line: 1 terabyte of SharePoint storage, plus 10 GB extra for each licensed user.

For a 50-person company, that’s a comfortable 1.5 TB.

For a 2,000-seat enterprise, it’s 21 TB. Sounds generous. Until it isn’t. 

What most admins discover one quiet Tuesday is that the pool is gone. Teams recordings, OneDrive sync gone sideways, six rounds of version history on every PowerPoint, a 2018 acquisition’s sites that nobody owns anymore — the storage is full, and Microsoft is asking $200 per terabyte per month for more. That’s $2,400 per TB per year. Negotiable on EA, sure. Still meaningful at 20 TB over the line. 

The math is unforgiving 

A typical mid-market tenant — 500 users — gets 5.9 TB included.

At a relatively modest 25 GB per user (Microsoft’s own benchmark for “well-used”), the actual SharePoint + Teams footprint sits at 12.2 TB. That’s 6.3 TB over the line, $15,000 a year you didn’t budget for, paying to hold a copy of a 4-year-old all-hands recording nobody has watched since 2021. 

Why it happens 

Storage growth in M365 is invisible to the people generating it.

End users record meetings, save attachments to SharePoint, drop video into Teams — every action adds to the bill, but the bill is paid by IT.

The feedback loop is broken. Without active intervention, every tenant trends toward “full” within 18–24 months of crossing the included pool, then keeps growing at roughly 30% year over year. 

Why “just buy more” loses on the spreadsheet 

Storage is recurring.

Every extra TB you provision today is $2,400 you’ll pay every year, indefinitely. A 25% cleanup — well within TSO’s expected delivery range — pays for itself in the first quarter and keeps paying every quarter after. 

It’s the rare optimisation where the ROI compounds. 

What’s reclaimable 

Five categories cover roughly 80% of typical excess: 

1. Teams meeting recordings older than 90 days. Nobody re-watches them; retention policies usually allow deletion. 

1. Version history bloat on heavy files. Office documents accumulate dozens of versions; most can be capped at 5–10. 

1. Orphaned sites with no listed owner. The Contoso demo we built for TSO had 102 of them out of 200 sites — about 51%. Industry average is closer to 30%. 

1. Duplicate content. Same file uploaded by different people, same library copied across sites. 

1. Large media sitting in libraries that were never meant for it — onboarding videos, conference recordings, marketing reels. 

A scan that walks every site and surfaces the candidates is the first step. Acting on the recommendations is the second. Most organisations have the second covered — what they’re missing is visibility into what to act on.