The "Personal backup" pricing plan is $99 USD / year and includes "Unlimited data backup" and "one year version history" which implies they are storing much more than just your data at a given time.
$99 would give you 5-6TB of data for consumer HDD costs. And then factor in that they are likely doing some type of additional backup/RAID it would be even less data per dollar. And that's not including maintenance, rent, and employees.
Disclosures: I’ve been a customer for almost a decade. I’m also an early (IPO) shareholder. I’ve never been employed by, or been a vendor to Backblaze.
To add some context and background —
Their “unlimited” plan has a few major capacity-saving caveats. For example, there are built-in exclusions you can’t modify to prevent the cruft and temporary files of supported OSs (and several common apps like Outlook) from taking up space. Backblaze Computer Backup won’t backup certain kinds of data like Time Machine backups on Macs. They also have an automatic policy of deleting backups of external drives that haven’t been connected to the backup host for 30 days. They have a long list of caveats that to their credit they do disclose, although it’s a bit hard to find and understand if you aren’t technical and aren’t looking.
Their backup service is built on their object storage infrastructure to prevent duplicating their own stack, and it also compresses the amount of overhead and capacity accounting they have to worry about between their two product lines. They don’t keep backups of customer data, but they’d need to suffer multiple hard drive and host failures effecting the same file at the same time to lose any single file. Their architecture is proprietary, which I expect adds a lot of human/payroll overhead they wouldn’t have if they just deployed endless ZFS pools “off the shelf”. They build their own servers which offsets the costs of going COTS from a vendor like Dell.
$99 would give you 5-6TB of data for consumer HDD costs. And then factor in that they are likely doing some type of additional backup/RAID it would be even less data per dollar. And that's not including maintenance, rent, and employees.
Honestly I'm surprised they exist