A nightly batch/analytics job runs on 4× m5.4xlarge On-Demand, 24×7, even though the work only runs off-hours and can safely restart if an instance disappears.
Targets (relaxed): p99 ≤ 300 ms, 99.0% availability, standard durability, under $300/mo.
Interruptible batch work is the textbook case for Spot instances, and there's no reason to run 24×7 — set a nights/weekends schedule, downsize to a right-sized Graviton class, and keep backups on the results database.