its honestly probably MORE expensive than just getting a hard drive-- verbatim has a 25 pack of 25GB discs for $33, or a ten-pack of 100GB from Sony for $55-- but the upfront cost is less, so it might make more sense?

i guess it depends on how likely it is for hard drives to go down in price in the near future...

@emaytch have a spreadsheet for computing the trade-offs for various kinds of add-only storage/backups. I haven't updated it in a few years, but from back then:

- Rotational hard disks were cheapest up to about 4TB of data.
- BD-R was then cheapest up to 150 TB.
- Above about 150 TB, it's LTO.

I factored in lifetime of equipment, and up-front costs (like BD burner).

The BD-R/LTO boundary was fairly loose, depending on which gen of LTO you got, and what the LTO second-hand market looked like.

@emaytch TBH, I'm surprised that HDDs have remained (or become) competitive, even at small volumes.

The fixed cost of a BD-R drive was pretty small (£50, last time I looked), and from what you said, it doesn't look like the price of the disks has changed much.

I think HDDs have gone *up* in price.

Remember that an HDD will only last for ~3-5 years (check the warranty period), and factor that in for replacement costs. BD-R disks should last for a good 10 years before needing to be replaced.