37Signals has a large AWS bill. About $3.2M USD last year. It sounds like they have been proactive at managing the bill and that’s just what it costs to run their business on AWS.
They are an interesting and smart company and it seems they are going to try to move some/most of that out of AWS. Dell will be happy to hear that but I don’t know if it will result in significant savings because you now have to hire and manage people to run the show robustly (especially the 8PB of storage).
At a minimum, they might consider some alternates for AWS S3. I have much smaller data needs, but find that iDrive works great and claims pricing that is 85% less than AWS S3. I don’t know if that would work for 37Signals but there have to be other storage providers out there than could provide solid reliability and cost savings.