I currently store 10 TB on my NAS, and growing. The data is live, I access some of it every day, sometimes remotely. I have 3 rotating "independent" backups in addition to the NAS (by independent I mean they're made with rsync and don't depend on any specific NAS OS feature), stored in an old safe that would probably not be very effective against thieves but should protect the drives in case of fire.

There are no recurring costs to this setup except electricity. I don't think S3 can beat that.