This looks like it is directly pointed towards AWS EBS and EBS PIOPS offerings so here some quick cost comparisons:

- Rackspace standard storage vs AWS EBS (for 1TB of storage with 100 IOPS) -- AWS US-East = $126/month -- Rackspace USA = $150/month

- Rackspace SSD vs AWS PIOPS (for 1TB of storage with 1000 IOPS) -- AWS US-East = $225/month -- Rackspace = $700/month

http://blog.planforcloud.com/2012/10/cost-comparison-rackspa...