I use https://www.jungledisk.com/ and have for a while now. I've tried mozy and a few others but jungle disk wish the cheapest one that let me back up data on a NAS. I think I pay $2.00 a month for Jungle Disk proper and then whatever the AWS usage fees are. I can't remember how much data I have up there but it's a good amount and I usually pay less than $10.00 a month. I also use the same account on multiple machines.