The people that keep saying "SSDs already existed huehuehue" don't have a grasp on how customized the PS5 SSD is and how fast it is
Okay. Wanna know why I laugh at the idea?
The Gigabyte AORUS NVME is the fastest SSD on the market right now. It uses NVME bus, optimized custom controller, firmware and it's own RAM for cache. The 1 TB stick
costs $271 and it reaches a top speed of... 4.9 GB/s in sequential read, and 4.2 GB/s in write.
Ok, let's suppose that Sony created its own controller for the SSD (a la Apple T2 chip) and gets a bit more performance from the NAND memory than the competition (otherwise they'd have to license the technology from Gigabyte or Samsung) : do you honestly think they can still get their R&D AND material costs to even less than $150 per-drive? (assuming the PS5 would cost $450)
Right...let's say that they managed to get the cost down. How will they handle the heat? Because unlike previous generation, NVMe SSDs tend to get hot (and a lot) and need proper cooling, otherwise they start losing performance. Sony already said they have a special solution for the APU...but haven't spoken about the entire chasis.
Lastly, let's say they've overcome all those issues. They have to take into account the random IOPS the drive is going to have to handle. Even if the theoretical speed is 5 GB/s, there is no way in hell that speed will be achieved, as that is sequential reading and most games don't use files that are large enough to actually reach that speed. In fact, games use a lot of smaller files (such as textures, sounds, etc) that are stored randomly in different places. If anything, the reading performance in games would be pretty much like the ones in the Xbox Series X.