That could be a lot of liability they're holding, since they voided the warranties on the externals by shucking them. So they could wind up paying twice for failed HDDs = $130 + $130 + $25 in gas and wage to pay someone to drive around to pick these up = $285 or so per HDD?
Failure rates are still likely to be low (<5% per annum)
I've only ever bought five external drives in my lifetime. Incidentally, all of them have been "shucked" over the years, and none of them have failed. They vary from 3-5 years old.
In fact, the only two drives I've had fail on me were OEM packaged, so based on my anecdotal, statistically insignificant personal experience you could even say the opposite, that external drives are more reliable than their OEM counterparts.
You never know. Perhaps the additional packaging prevents damage to the drives in transit, and the process of installing software on the drives (as I believe some manufacturers do with external drives) provides another opportunity to quality check the drives.
*Yev from Backblaze here: I can now purchase from Costco again, so all is well on that front. Even with a price at or around your calculated $285, that is still half as expensive as the $600 per drive we were once quoted during the crisis.
Plus 2 people got banned from Costco.