They don’t have great North American peering. If you happen to be there and are unlucky, you won’t be able to get a very reliable/fast connection to the server.
I tried to use one for Borg backups a few years ago and just ran into endless transient connection issues.
It's more like $2 a TB in the larger plans. I have 5TB there and it's been working great. I use Borg Backup so the data is all encrypted. If anyone cares, Digital Ocean also makes new customers send their ID.
For stuff like archive and backup you can use ovh object storage infrequent access. Comes to 5$ per GB but you pay for what you use only and it scale infinitely.