Run them all in parallel with a cloud function in less than a minute?
I've heard from people running 100+ prompts in parallel against it.
https://ai.google.dev/pricing#1_5flash
4o-mini's rate limits scale based on your account history, from 500RPM/200,000TPM to 30,000RPM/150,000,000TPM.
Really it boils down to balance of time and cost, and the skill set of the person getting the job done.
But you seem really anti establishment (hung up over $25 cloud spend), so you do you.
Just don't expect everyone else to agree with you.