This makes a lot of sense. After all, NAND flash, which makes up the bulk of the cost of an SSD is renowned for its rapidly-falling prices.
The short answer to this question is: “Never!”
Although NAND flash prices are indeed dropping at an amazing rate, HDD capacities are increasing at a similarly amazing rate. Given that the typical high-volume HDD sells for a relatively static $50 it’s easy to derive an average cost per gigabyte for HDDs and plot that against the price per gigabyte of NAND flash, which is exactly what we did in the graphic for this post.
This chart, assembled with data provided by PriceG2, an HDD and SSD price tracking service, plots average NAND and HDD price per gigabyte from 2004 to 2011. It originally appeared in the Objective Analysis report – How PC NAND Will Undermine DRAM – which can be ordered directly from the Objective Analysis website.
The chart uses a semi-logarithmic format, in which constant growth appears as a straight line.
Note that the HDD (black) and NAND (red) lines are roughly parallel. This translates to a 20:1 price difference between NAND and HDD over the entire 7-year course of this chart. There is no reason to anticipate any dramatic changes in the future. The lines should not converge, and SSDs will always command a higher price than HDDs.