When we looked at the future of solid state disks back in July, we spent some time discussing an ominously titled research paper from the University of California-San Diego and Microsoft called "The Bleak Future of NAND Flash Memory." The paper made a number of well-supported conclusions about the end-state of NAND flash, the type of flash powering today's solid state disks, but one area where it misstepped was on pricing—the paper was released at a time when SSD prices had flattened.

A few months later, though, prices on solid state disks entered a free-fall. Computerworld has a report examining the current pricing trends, noting that in spite of the short period of flatness in 2011, SSD prices are down more than 66 percent over the past three years. Computerworld notes that consumer SSDs were typically coming in at about $3 per gigabyte in 2010, whereas today it is common to find SSDs clocking in at under $1 per gigabyte. That price point, $1 per gig, seems to be the magical tipping point for most folks—at or below that mark, SSDs begin to look like much more reasonable purchases.

A quick survey of several online merchants shows popular brand and sizes, like the 256GB flavor of Crucial's SATA III M4 SSD, coming in at more like 80¢ per gigabyte, while even higher-priced disks like the Intel 520 are hovering slightly above the $1/GB mark. It's so easy to get a cheap and fast SSD that we've even recommended solid state for our "Budget Box" in our December 2012 System Guide. This is definitely a first, but the pricing and performance are worth it.

The Computerworld report quotes a blog entry from earlier in the year at Dynamite Data, noting that "[w]e're currently experiencing the fastest decline in SSD prices in three years. If history has anything to say we will now see prices per drive stabilize and the size of the drives substantially grow over the next few years." This conclusion jibes with the UCSD/Microsoft paper, which predicts that TLC NAND—that is, triple-level cell NAND, where each flash cell stores three bits in eight discrete voltage levels—will top out at a 6.5nm process size and hold a maximum of 1,700GB per chip. An eight-chip drive, as is common today, would wind up with a raw capacity of 14TB.

That kind of scaling doesn't come without its own issues; read latency rises as process size shrinks, but the reduced cell life brought about by TLC NAND means that any drive at that size and density would have to have a tremendous amount of oversubscription to make up for failing cells. Recent advances in high-temperature NAND annealing might mitigate that problem, though. NAND density of this level is still at least ten years off, so the discussion is mostly academic, but it won't be that way forever.

It's difficult to say for certain if SSD pricing will ever drop to the level of hard disk pricing, where 5-10¢ per gigabyte is common. If the current trends continue, though, and SSDs continue to cost roughly the same on a per-drive basis even as capacities increase, $1/GB will definitely no longer be the metric for an "affordable" SSD. Enterprise SSDs are currently priced far higher (in part due to the technologies inside of them and in part due to businesses simply being willing to pay more), but we may soon hit a point where $1/GB is an acceptable enterprise SSD cost and consumer SSDs are far, far less.