Do Data Online Backup Services Charge a Lot of Money?

I love all the opportunities that have been opened up as the internet has become more popular. Now I hear that you can do data online backup in order to save a copy of your important information away from your home. People have told me it is pretty easy to do, and that there are safeguards in place to keep your data private. However, I am not sure whether or not this would be something that I could afford to do. Is this type of thing expensive? I think I might look into it just because it looks like a useful service.