Hard disk drives are cheaper because they have extremely low cost of manufacturing. The aluminum/glass platers with magnetic layers are less than US$5 per piece. Add the read/write head which cost like super cheap (less than US$3) as they are all mass manufactured on a single wafer before they are diced into individual heads. Other significant parts are the spindle motor, voice coil motor, E-block assembly, hard casing, etc; these don't cost a lot. The profit margin on your hard disk drives is still rather large. The main selling point of Hard disk drives is the larger capacity, offering cheaper dollars per Gigabyte when compared to SSDs.
Will we reach a state where most HDD in future products, are replaced by SSD in, say, 5 years' or 10 years' time? :dunno:
Link http://techon.nikkeibp.co.jp/article/HONSHI/20090528/170920/article linked above part 3 said:There is, however, a problem that still has to be overcome before SSDs can achieve that future growth. Evolution toward lower cost will be made possible by finer manufacturing technology, multi-level architecture and other advances, but these changes will also degrade NAND Flash memory quality.
NAND Flash memory quality is also beginning to drop. Chips manufactured using 90nm-generation technology in 2004-05, for example, were assured for about 100,000 rewrites and data retention of about a decade. As multi-level architecture and smaller geometry are introduced, quality is showing a sharp decline. The 30nm 2-bit/cell chips expected to enter volume production in 2009-10 may well end up with a rewrite assurance of no more than 3,000 cycles, and a data retention time of about a year. The first 3-bit/cell chips are hitting the market now, with only a few hundred rewrites.
Simply because HDD manufacturing is more matured than Flash memory production.
If the manufacturers shift their attention to SSD and invest more in it's research, and spend less effort on HDD, then SSD may reach comparable pricing with HDD. If they continue to invest equal effort on both, it'll be quite far away for the SSD to reach similar pricing with HDD on a cost per GB basis..