"General Purpose (SSD) volumes provide the ability to burst to 3,000 IOPS per volume, independent of volume size, to meet the performance needs of most applications and also deliver a consistent baseline of 3 IOPS/GiB. Provisioned IOPS (SSD) volumes can deliver up to 4000 IOPS and are best for EBS-optimized instances. Magnetic volumes, previously called 'standard volumes', deliver approximately 100 IOPS on average, with a best effort ability to burst to hundreds of IOPS."
The EBS Pricing page (http://aws.amazon.com/ebs/pricing/) currently makes no mention of General Purpose (SSD) volumes.