In March of 2008 MSRP for OCZ's 32GB drive was $500, and $1100 for their 64GB variant. Now OCZ's best 32GB drive is about $150, and it's about $260 for the 60GB Vertex Turbo.
So prices have dropped about 70% since March 2008 for drives of the same capacity, but performance has increased significantly. I easily expect another 50% decrease within the next 4-6 months as people s-l-o-w-l-y migrate towards SSD's and new faster drives are developed, causing the older drives prices to plummet.