It looks like Amazon Web Services has come up with a new tiered pricing system.

Dear Amazon Web Services Developer,

As you know, our goal is to drive down our costs relentlessly, and to pass on those savings to our customers in the form of lower prices. Amazon S3 has grown rapidly, now housing over 29 billion objects, and we’ve been able to make the service even more efficient. Six months ago, we lowered outbound transfer prices. Today, we’re pleased to announce new storage pricing tiers. This new pricing structure means that your costs will continue to decrease over time as your storage increases. These changes will be effective November 1, 2008.
Current storage price (through Oct 31, 2008)
US: $0.150 per GB
EU: $0.180 per GB

New storage price (effective Nov 1, 2008)
US
$0.150 First 50 TB / month of storage used
$0.140 Next 50 TB / month of storage used
$0.130 Next 400 TB / month of storage used
$0.120 Storage used / month over 500 TB

EU
$0.180 First 50 TB / month of storage used
$0.170 Next 50 TB / month of storage used
$0.160 Next 400 TB / month of storage used
$0.150 Storage used / month over 500 TB

Please see http://aws.amazon.com/s3 for full Amazon S3 pricing info. Thank you as always for your support.

Sincerely,

The Amazon S3 Team

Seems to be a bit more affordable over the long haul.