These prices make the new Standard-IA storage significantly cheaper than the Reduced Redundancy Storage, even if you end up reading the data back.
However, I find it interesting that in addition to the cost per GB to retrieve data, this new storage class also has a significantly higher per-request cost, too. Actually, it looks cheaper to upload an object as a different storage class and then transition it to Standard-IA, since PUT of IA costs $0.01 per 1000, but PUT of another class costs $0.005 per 1000, and the cost to transition another class to IA is $0.01 per 10000. It's a small difference ($0.04 per 10k objects), but if you store an obscene amount of data on S3, that seems like enough difference to matter.
I'm going to go out on a limb and guess that Standard-IA is basically Standard except with slow disks instead of fast. Slow disks have lower $/GB, but higher $/IOPS.
Seems unlikely, given some of the other properties it has; more likely, Standard-IA has fewer copies of the data, and then a backup in Glacier, which explains why it has high durability but low availability.
Doubtful. Almost certainly the same storage backend, but IA requests are more aggressively throttled, so there's more chance of requests being rejected. S3's capacity planning then requires less request processing infrastructure to serve IA, so it's cheaper to provide than regular S3.
However, I find it interesting that in addition to the cost per GB to retrieve data, this new storage class also has a significantly higher per-request cost, too. Actually, it looks cheaper to upload an object as a different storage class and then transition it to Standard-IA, since PUT of IA costs $0.01 per 1000, but PUT of another class costs $0.005 per 1000, and the cost to transition another class to IA is $0.01 per 10000. It's a small difference ($0.04 per 10k objects), but if you store an obscene amount of data on S3, that seems like enough difference to matter.