Deleting data from Amazon Glacier is free if the archive being deleted has been stored for three months or longer. If an archive is deleted within three months of being uploaded, you will be charged an early deletion fee. In the US East (Northern Virginia) Region, you would be charged a prorated early deletion fee of $0.03 per gigabyte deleted within three months.
So I guess that means it would still work well for a scheme like time machine uses, where incremental changes are added but deletions are simply made note of. At least I think that's how it works.
Deleting data from Amazon Glacier is free if the archive being deleted has been stored for three months or longer. If an archive is deleted within three months of being uploaded, you will be charged an early deletion fee. In the US East (Northern Virginia) Region, you would be charged a prorated early deletion fee of $0.03 per gigabyte deleted within three months.