Licence savings are the headline. The real numbers sit in re-architecture, egress, and the six months of parallel running nobody budgets for.
Cloud business cases tend to compare a server invoice with a cloud invoice. That comparison is almost always wrong, because it prices the destination and ignores the journey.
The three costs people miss
Parallel running. Old and new systems both run during cutover — often for two or three quarters.
Re-architecture. Lift-and-shift preserves your bottlenecks and your bill. Anything that genuinely benefits from cloud economics usually needs redesign.
Data movement. Egress and cross-region traffic are small line items until a badly placed pipeline makes them large ones.
How to build a defensible case
Price the migration and the steady state separately, attach each saving to an owner, and agree what you will switch off. A migration with no decommissioning plan is an expansion, not a migration.
