Their margin on bandwidth is literally over 1000%. Quick google says that S3 costs 320% more than Backblaze (which, presumably, isn't running at a loss).

> At a guess

The comments in this discussion that try to provide actual numbers show a fairly lopsided argument against S3. The comments that are advocating for S3 aren't as detailed.

You can look at this at the macro level, as on comment did, and see that one 1.2PB RackmountPro 4U server is $11K. Yes, of course you still need space and power. But at least this gives us actual numbers to play with as a base (e.g. buying 10 of these is less than what you'll spend on S3 in a month)

At a miro-level. You can spend $650 on a 16TB hard drive, or $650 on 16TB for 2 months of S3. Now, S3 is battle-tested, has redundancy, has power, has a cpu, has a network card (but not bandwidth), and is managed - unquestionable HUGE wins. But the hard drive (and other equipment) come with a 3-5 year warranty. Now, the difference between $650 for the hard drive, and $12000 for S3 over 3 years, won't let you: get the power, rent the racks, hire the staff, and invest in learning ceph. But the difference between $400K and $5million will.