Are you planning to build sth on top of Glacier or include Glacier as an storage option (seeing it's on S3 anyway)? It will bring the cost down a great deal.
Many of us have alternative backup solutions. Like I use CrashPlan to backup pretty much everything and the most important files are backed up also to my external hard drive and a friend's machine (all via CrashPlan). Having said that I still consider I've only one off-site backup that is CrashPlan servers and though they provide excellent service they have failed many times before and hence I need an insurance. My entire laptop (except OS and apps) glaciated by Tarsnap can be that insurance policy which I'll most probably never access anyway, until when My laptop and all those three backup destination fail at once and in that scenario I will be willing to pay that cost seeing I saved a lot during those years/months.
I got started because I wanted good backups and there were no solutions available which I was satisfied with.