The differences stack up for say, a 1GB video that becomes viral and triggers terabytes in egress. You pay for 1GB, not terabytes.
It’s also an optional tier.
Under the condition that you actively monitor the usage and manage to "process it once" on time (and then "process it back"). Because otherwise you pay for terabytes - not in egress fees, but in processing fees. Or am I missing something?
All object stores out there have a flavor of IA class with an access fee that should be far lower than the storage class savings for scenarios where you would even consider using this. If you don't want or understand this cost optimization you simply don't use it.