The total still depends on actual time taken, but the rate does not. Paired with an honest estimate of hours, it gives a clear basis for budgeting without the buffer built into most fixed prices.
Where this term comes up
Cite: Sydney Relocators, "Locked-in hourly rate", Removalists in Sydney, reviewed 2026-11-08, https://removalistsinsydney.com.au/glossary/locked-in-hourly-rate/