Good point about where the extra SSD is located.
Another point in regards to an extra SSD/NVMEdrive for the PS5 is that on the PS5 motherboard, theres 6 SSD chips (3 on each side), and there is some space in between them. On a NVME-drive, these chips are likely a bit closer together, which might produce a bit more heat due to that. I'm very curious to see how much more noisy a PS5 will potentially be due to inserting an extra SSD. Personally, i'm not expecting that much more noise to be honest, but i could see it being a bit louder.
Looking at NVME-drives with similar read/write speed for PC, its around $230 - $250 for 1TB. I expecting it to be the same for PS5 considering that these drives are the same that PCs uses. I'm curious how things will be distributed though. I mean, will each manufacturer mark their drives as "PS5 compatible" and/or will Sony have a list on their website showing which NVME drive that is fast enough and can be used on a PS5.