Quantify the time Resource Manager saves over manual provisioning, including drift detection, and cost the difference.
The saving is the difference between two effort models, each inflated by its own rework rate, because the real benefit of a Terraform stack is not the apply itself but the changes you do not have to redo. Drift detection is charged against the automated side as an honest overhead — it is work that manual provisioning simply never does. Resource Manager carries no service charge, so the business case is entirely about engineer hours and error rates, and quantifying the rework rate is what makes the argument credible. You still pay full price for whatever the stack provisions, which is why the resources themselves belong in the compute and storage calculators.
OCI Resource Manager
manual hours = runs × manual minutes × (1 + manual rework %) ÷ 60; automated hours = runs × run minutes × (1 + automated rework %) ÷ 60 + drift-check hours; saving = (manual − automated) × engineer rate.
manual hours = runs × manual minutes × (1 + manual rework %) ÷ 60; automated hours = runs × run minutes × (1 + automated rework %) ÷ 60 + drift-check hours; saving = (manual − automated) × engineer rate. The saving is the difference between two effort models, each inflated by its own rework rate, because the real benefit of a Terraform stack is not the apply itself but the changes you do not have to redo. Drift detection is charged against the automated side as an honest overhead — it is work that manual provisioning simply never does.
Resource Manager carries no service charge, so the business case is entirely about engineer hours and error rates, and quantifying the rework rate is what makes the argument credible. You still pay full price for whatever the stack provisions, which is why the resources themselves belong in the compute and storage calculators.
This calculator takes 10 inputs: Stacks under management, Apply runs per stack each month, Manual effort per change, Effort per Resource Manager run, Drift detection runs per stack, Effort per drift check, Manual changes needing rework, Automated changes needing rework, Loaded engineer rate, Resource Manager service charge. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.