"Starting October 1, 2016, we will begin charging for snapshot storage at $0.05 per gigabyte per month. This will first be reflected in the invoice posted to your account on November 1, 2016. Like other features, snapshot storage uses hourly pricing, and size is calculated from a compressed version of the snapshot—not the total disk space allocated to the Droplet."
I see a problem with this method stemming from the way that snapshot sizes are calculated:
"Our snapshot sizes are determined on the size of your Droplet's sparse disk image, and any data that is added to your server and then deleted will still remain in the disk image unless the disk has been zeroed out to reclaim this image size.
When you delete files inside the droplet, that simply marks the space available again, but doesn't zero out the space in the underlying disk image on the physical server. Snapshots are compressed, though, so you could try using a program like zerofree while the Droplet's disk image has been mounted read-only (such as through our Recovery ISO) to see if that has some effect"
This seems to be quite confusing and possibly not feasible for many customers. This is my suggestion: I would much rather there be a threshold before being charged. So, maybe only charge for storage after, say 15GB. So, if I have some snapshots that total 20GB, I would only be charged for 5GB over threshold. I mean seriously, storage is ridiculously cheap these days. I'd much rather see snapshots preserved as a value-added service.