TCO worksheet: what the quote leaves out

Nine cost lines the vendor will not put in the proposal, with how to estimate each.

The subscription line is the most visible number and rarely the largest. Fill in these nine lines before you compare quotes; the TCO calculator does the arithmetic.

Line	How to estimate it
Implementation	Vendor professional services quote plus your own engineer's hours for the first ninety days. Reference customers will tell you the real number.
Internal run effort	Hours per week for tuning, alert triage the product creates, upgrades, and vendor calls. Ask two customers. Multiply by a loaded hourly cost, not salary.
Renewal uplift	The percentage the vendor raises price each year. If it is not in the order form, assume 7 to 10 percent and negotiate it in.
Add-ons	Modules most customers buy in year two. Ask the account manager which three add-ons their customers of your size most often buy.
Overage	What happens when you exceed the unit count: endpoints, users, GB per day. Price the scenario where you grow 20 percent.
Infrastructure	Collectors, sensors, storage, egress for telemetry leaving your cloud. Log products are the usual surprise.
Training	Vendor courses, certifications, and the time people spend in them.
Integration upkeep	Every connector to identity, ticketing, and SIEM breaks at some point. Budget a few days a year.
Exit	Data export, running two products in parallel during a migration, and re-tuning the replacement. Budget one quarter of a subscription year.

Two rules of thumb

If internal run effort is under two hours a week, someone has underestimated it.
Compare per-seat-per-month across a three-year horizon, never year-one list price.

Read the order form, not the proposal

Uplift, overage, auto-renewal, and notice period live in the order form and the master agreement. Proposals are marketing.

Published 6 Sep 2026. Free to reuse inside your organisation with attribution to DBSE.