I was actually fearing worse since proprietary systems are always expensive, but yeah, it's still very expensive.
For the speed of the SSD in the XSX, PCIe 3.0 is plenty fast enough. For the PS5 SSD, a PCIe 4.0 connector would be needed, but not the one in the XSX.
As such, you can compare with any NVMe SSD with both read and write speeds (both to give Microsoft the benefit of the doubt) over 2400 MB/s, which is the supposed speed of the XSX SSD.
Hum yah, 4.8 is "compressed". So PCIe 3.0 can achieve it. Price would be lower then