I mention the fee sometimes payable on delivery when using SF Express not because it's exorbitant but because it often comes as surprise to the recipient, who was expecting just a package, not a package and a bill.
The shipper can select when they ship the package. From a receiver standpoint, the shipper can stick it to you without you knowing (technically) if they simply check on the "paid by receiver" box on the bill. But then this is more about integrity.