With these being highly customized SSDs it's unlikely they'll be using an off the shelf SSD controller. That means economies of scale won't be there for that custom bit of silicon, so the controller is going to be significantly more expensive than what an SSD maker would expect to pay. Consoles sell in miniscule numbers compared to even the worst selling SSD controllers. And the worst selling SSD controllers are often the most expensive as they are targeted at niche segments like data centers.
Also, since we don't know what exactly comprises their solution for faster SSD data access and streaming, it's entirely possible that it could be using a larger pool of DRAM cache, further increasing the cost of the SSD solution.
Considering how game asset loading times could potentially affect game graphics more than increasing GPU silicon space per USD spent, we could see more spent on the storage solutions with less spend on the SOC. This would lead to potentially disappointing specs for console warriors but a greater increase in game visuals than spending more on the SOC.
Some people look at this generation as potentially being "boring" due to how similar the SOC will be between the next PlayStation and Xbox, but (IMO) this could potentially be the most interesting as we could see greater emphasis on something that only indirectly affects the graphics that are displayed. However, that indirect effect is potentially massive and something that hasn't been previously explored.
Regards,
SB