The real cost of per-seat email at 5, 25, 100 people

Most business email is priced per user per month. Google Workspace Business Starter is $7.20/user/month. Microsoft 365 Business Basic is $6/user/month. Fastmail Standard is $5/user/month. Zoho Mail Lite is $1/user/month. The differences are real; the shape of the pricing is identical.

That shape has consequences beyond the sticker price. Some of them are obvious (more people = more cost). Some of them aren't. Here's the unbundled view of what per-seat email actually costs once you account for the things teams stop doing — or start paying for separately — because per-seat pushes them into it.

The sticker math

We'll use Google Workspace Business Starter as the reference because its pricing is most public, and the patterns extend to every per-seat host.

5 mailboxes    × $7.20/mo × 12 = $432/year
25 mailboxes   × $7.20/mo × 12 = $2,160/year
100 mailboxes  × $7.20/mo × 12 = $8,640/year

That's the line in your accounting software. It's not the full picture.

Hidden cost 1 — Role addresses become seats

Per-seat hosts mostly let you have role aliases (sales@, support@) without charging extra — as long as the alias points to an existing seat. The problem is the shape of what teams actually want:

• A shared support@ inbox where 3 people can read and reply: typically requires a dedicated seat for the shared mailbox, plus delegation features, plus often a tier upgrade
• A legal@ address that needs its own retention rules and history: typically a separate seat
• An oncall@ rotation: either configured as a Google Group (free) or a dedicated seat depending on whether you need historical context

The realistic cost: each non-trivial role address that needs its own history adds roughly one seat. A 25-person team with sales@, support@, careers@, legal@, press@, billing@, security@, oncall@ is paying for 33 effective seats, not 25.

At Workspace pricing: that's 33 × $7.20 × 12 = $2,851/year instead of $2,160. ~32% above the sticker.

Hidden cost 2 — Ex-employee mailboxes

The legal / compliance reality is that you can't just delete an ex-employee's mailbox the day they leave. You typically need to:

• Retain it for 30-90 days for handoff
• Retain it for 1-7 years for legal/regulatory reasons depending on industry
• Keep it accessible for occasional reference

Per-seat hosts charge you for retained mailboxes the same as active ones. Workspace's Vault tier (for retention) is additional at $4-8/user/month depending on level. So a leaver costs you:

• The remaining seat fee until you formally close the mailbox (often ends up being months)
• Plus Vault retention fees if you have any
• Plus the operational overhead of remembering when to delete

At a 25-person team with normal turnover (10-15% annually = 3 leavers/year), you typically have 2-4 retained mailboxes on the books at any given time. Roughly $200-350/year extra.

Hidden cost 3 — Storage tier upgrades

Workspace Business Starter ships 30 GB per user. The next tier (Business Standard) ships 2 TB and costs $14/user/month — almost double. The tier upgrade triggers the moment one person needs more than 30 GB, because Workspace bills per-tier across the whole org, not per-user.

The honest version: 30 GB is enough for the first few years. Then your customer-success person who archives every email hits 30 GB. Now you're either deleting their archive (uncomfortable conversation) or upgrading the whole org to Business Standard.

For a 25-person team going Business Starter → Business Standard: 25 × ($14 - $7.20) × 12 = $2,040/year extra to accommodate one person's storage. Per-seat compounds tier upgrades.

Hidden cost 4 — The things teams stop doing

Less measurable but very real. When email costs $7-12 per person per month, organisations start optimising:

• Role addresses that should exist don't. "Do we really need a separate security@?" Yes, you do; security researchers expect it. But there's a $7-12/month opportunity cost on every conversation about whether to add one.
• Contractors and short-term collaborators get personal Gmail addresses instead of company aliases, because creating a seat for a 6-week engagement is awkward to justify.
• Internal tools that send mail (status pages, alerts) get configured to send from a single shared address rather than per-system addresses, because each one needs a seat.

You don't see these on the invoice. You see them in the worse architecture they create.

The three-year total

Putting the four together for a 25-person team on Workspace Business Starter, assuming average growth and turnover:

Year 1
  25 sticker seats        $2,160
  8 role-address seats    $691
  3 retained ex-employee  $260
  storage tier upgrade    $2,040 (triggers Q3)
  ─────────────────────────────────
  Year 1 total:           $5,151

Year 2
  30 sticker seats        $2,592   (growth)
  10 role-address seats   $864
  4 retained ex-employee  $346
  storage tier (Standard) $5,040   (full year on Business Standard)
  ─────────────────────────────────
  Year 2 total:           $8,842

Year 3
  35 sticker seats        $3,024
  10 role-address seats   $864
  5 retained ex-employee  $432
  storage tier (Standard) $5,880
  ─────────────────────────────────
  Year 3 total:           $10,200

3-year total: $24,193

The sticker total was $7,776 (25 + 30 + 35 × $7.20 × 12). The realised total is 3.1× the sticker — not because the host is dishonest, but because per-seat pricing pulls a bunch of decisions into your control where they'd otherwise be defaults.

The flat-rate alternative

Same 25→35 person team on a flat-rate plan ($50/year flat, unlimited mailboxes):

Year 1: $50
Year 2: $50
Year 3: $50
3-year total: $150

Storage add-ons might push that to $200-400/year depending on archive size. Even at the high end, you're talking ~$1,000 over three years versus ~$24,000. That's not a slightly-better deal; it's a different category of expense.

When per-seat actually makes sense

Honest answer: per-seat pricing isn't always worse value. It makes sense when:

• You genuinely use the bundle. If your team lives in Google Docs / Drive / Calendar / Meet, the per-seat price is amortised across more value than just email. Workspace Business Starter at $7.20 is reasonable when the cost-per-feature is fractional across what you're using.
• You're under 5 people for the long term. Per-seat × small team is small absolute money. Optimising it isn't where your attention should go.
• Your IT/compliance team specifies the vendor. Some procurement processes effectively pre-decide email. Per-seat is the default; the cost is what it is.

Outside those, the flat-rate model usually wins past your second or third hire.

What flat-rate teams do with the difference

We see customers reallocate the saved money in predictable ways:

• A round of customer-support hires earlier than planned
• A real CRM (Notion → HubSpot, Linear → custom) rather than putting it off
• Marketing budget for a quarter that would otherwise have been "no, we can't"
• Or simply: lower runway burn, which is the most underrated outcome for an early-stage team

The numbers above aren't theoretical. They're the calculation we walk customers through when they ask "are we really going to save that much?" — and yes, mostly, they are.

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If you're working through this math for your specific team size, the comparison pages have worked examples for Google Workspace, Microsoft 365, Zoho Mail, and Fastmail side-by-side with Biza Email's flat plan.