It boils down to easier to manufacture the SSD than HDD. SSD, all you need is the Flash IC (which is made by several manufacturers) and Controller. Designing SSD is simple unlike HDD (I think you can actually retool RAM factory to SSD easily...). This principle applies to DRAM and DRAM-less SSD (some Flash NAND IC maker also make RAM IC). This results to local brand that used to sell phone chargers and power banks ended up selling SSD too, you can just hop to Alibaba, find right supplier, do some negotiations (custom branding, price, port of arrivals), and all you need is manage after sales service! Even a guy with no expertise in electronics could sell SSD, or system integrators (which I would do if I have large business for PC manufacturing, in house brand SSD for cheaper lineups.). On the other hand, HDD manufacturing must be accompanied with large investment (clean room, precision tools, etc). In the end, now there are only 3 companies involved: Seagate (purchased Samsung), WD (
