If you really want to utilize an old-school, but still viable method, of archiving data... utilizing a tape drive is generally more affordable on the per GB level than the 3.5-inch high-capacity floppy disk.
Floppy disks were effectively killed off by USB flash drives as they could store more data in a small space. It's difficult to find a usable USB Floppy drive & diskettes because they can wear out fairly quickly. Floppy disks can only hold 1.38 MB of data per diskette, meaning to store 1 GB... you would need 743 diskettes.
By comparison, CD-ROMs store up to 700 MB's of data (or 508 diskettes)... DVD-ROM stores 4.7 GB's (or 3,488 diskettes) for a single layer & 9.4 GB's (or 6,976 diskettes) for dual layer. BluRay discs can store up to 50 GB's (37,102 diskettes).
To backup a modern computer (w/ a 500 GB storage drive), you're looking at 371,014 floppy disks to do so while breaking large files across multiple diskettes. The major risk is that if one sector of a floppy goes bad (or more commonly, MULTIPLE sectors) while writing the file to the disk OR from degradation from reading, the file in question may become irreparably damaged. You're also look at a massive cost, even if you spend $0.10 / diskette, you're still looking at spending over $37,000 in the process... even if the USB disk drive only runs you $50.
As mentioned above, tape drives were created back in 1950's (floppies were created in the late 1960's) & surpassed storage capacity of floppies in the 1972 (running around 20 MB's at the time). Magnetic tape drives are still being developed & utilized for archival / backup purposes in present times, pushing storage capacity into multiple TB's per cassette / cartridge. While a modern tape drive will run up to $4,000 for the equipment & up to $100 for cassette... but the high capacity would mean you could backup multiple computers (w/ 500 GB storage drives) with one cassette. This could effectively drop the back-up costs to around $410 / computer.
Hope this sheds some light on the subject.