When Does IT Staff Augmentation Actually Make Sense Over Full Time Hires

[remotestateofficial]

Going back and forth on this decision longer than I probably should be.
We have a six month project that needs extra hands fast, but committing to full time hires feels risky if the workload drops off after the project wraps. Looking into IT staff augmentation as a middle ground but not entirely sure if it actually saves money once you factor in everything involved.
First time weighing this tradeoff seriously so want to hear from people who've actually made this call before.
A couple things I'm unsure about:
Whether augmented staff genuinely ramp up fast enough to be worth it for a short term project
How this compares cost wise once you account for onboarding time either way
If you've gone through this decision before, what made you pick one over the other?

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