It doesn't make business sense for Sony to undercut the Series X.
All the joking aside, the demand for the PS5 is higher than the demand for the Series X. If they are priced the same, most with a PS4, will go to a PS5. So Sony should just pocket that $100, and wait until sales slow to give a price cut. It is clear that Sony realizes that to stay the market leader they have to spend on content, so there is no need to come in below consumers willingness to pay for the console. That is an expense the market says Sony doesn't need to take on. $499, $450, seems like the logical move.