My 2.5inch 160GB SSD costs $1.875 per GB. A 2.5 inch 160GB 5400RPM costs $0.218 per GB.
Woah, that’s expensive! That SSD is 8.6 times the cost of the HDD. O but wait… take a gander at this little picture:
My SSD score is 8 times that of my old HDD. Which nearly matches the price difference. I’d attribute that extra 0.6 to additional reliability that SSDs provide.