Anyone operating at the scale of Backblaze should also already have the right infrastructure to deal with a drive, machine, rack, PSU, etc failure without causi

Anyone operating at the scale of Backblaze should also already have the right infrastructure to deal with a drive, machine, rack, PSU, etc failure without causing service downtime. (And NB that part of that will including diversifying between drive brands to guard against eg a firmware issue which affects many drives of a certain brnad in a limited time window). What matters in that context is something similar to $/GB x (% of drives which make it to end of useful life in their application context). Cheaper drives which are less reliable might well win on that score. They might also expect to retire drives rather sooner than an average NAS user as the power cost of running older, smaller drives becomes an issue. In an average small NAS setup the cost of a failed drive is potentially much higher. You incur at a minimum a performance penalty while the array is degraded and a significant performance penalty while it's rebuilding and have lower guarantees against data loss during that period and you can't average that out over thousands of drives.