What I'd like to do is find a service that's super simple and with low pricing where I can upload a few hundred GB of files that I almost never access, to serve as a kind of "self storage unit" of the files that I want access to if needed, and I want with somewhere that has good backups, but that way I can get the space freed up.
I don't want to use hard drives locally, I'd rather it be a cloud service.
Is Dropbox the best option ($10/mo for 2TB), or should I look at an S3 client like Cyberduck (though if I'm storing 1TB it'll be more expensive than Dropbox, it seems)?
Anyway Box Drive does what you want and has 10GB for free to play with.
AWS CLI is also dead simple to pick up for S3.