The Migration Quote Problem
A mid-market manufacturing company getting acquired needed to migrate from four Azure tenants to one. The vendor quote: £380K. Timeline: 90 days.
The actual migration cost at completion: £1.2M. Timeline: 7 months.
The vendor quote covered the cloud infrastructure migration. It didn’t cover identity cleanup required before migration could begin (12 weeks), SaaS contract restructuring the migration exposed (£140K), application remediation required when authentication paths changed (3 applications × 6 weeks of developer time), and the emergency DR architecture needed when production database cut over before DR was validated (£90K).
The quote was accurate for 40% of the actual work. The other 60% wasn’t in the quote because the vendor only saw the cloud layer — not the identity layer, not the application layer, not the contract layer.
The Full Migration Cost Model
Layer 1: Cloud Infrastructure (The Quote Layer)
What vendors miss: Non-standard VM configurations, storage tiers that don’t map cleanly, VPN dependencies requiring network team coordination outside the migration contract.
Actual vs. quoted: Typically 15-25% more.
Layer 2: Identity Infrastructure (The Hidden Layer)
What vendors don’t include: AD cleanup, service account remediation, Entra ID sync configuration, Conditional Access policy reimplementation, MFA and security baseline reconfiguration.
Actual vs. quoted: 20-40% of the cloud infrastructure cost.
Layer 3: Application Layer (The Unmapped Layer)
What vendors can’t quote without discovery: Applications with hardcoded Azure tenant IDs, applications that authenticate through a specific AD forest being deprecated, custom LOB applications with on-premise dependencies that aren’t documented.
Actual vs. quoted: From 0% to 200%+ of cloud infrastructure cost.
Layer 4: Contract and License Layer (The Liability Layer)
What nobody quotes: SaaS license reallocation, enterprise agreement minimum commitment penalties, hybrid infrastructure contracts that can’t be exited cleanly.
Actual vs. quoted: £50K-500K for mid-market, never in the migration quote.
The Discovery-First Migration Model
The migration companies that get this right run a discovery sprint before quoting. They separate the migration into two phases:
Phase 1: Discovery Sprint (2-3 weeks) — Complete estate inventory, application dependency mapping, identity infrastructure assessment, contract and license inventory, migration complexity scoring.
Phase 2: Migration Plan — Accurate timeline estimate, accurate cost estimate, phased wave plan, risk register.
The discovery-first model costs more upfront (typically £30K-80K) and results in accurate quotes. The alternative is a quoted migration that overruns by 3x and takes 4x as long.
Migration planning without a discovery sprint is guessing. ACQI runs the discovery sprint in 48-72 hours. Request a migration readiness assessment.