I gave up and just started using AWS S3 directly. I use a few GB, pay a few pennies for storage, a few more pennies for bandwidth if I'm moving stuff around, and that's it. I've never paid more than $10/month, and it's usually under $1/month.
But the argument for dropbox is that you have a client for almost every platform you can use. With S3 you'll have to use a 3rd-party software, which might not function properly.