Welp, he's been right about several things of late so there's a chance he could be correct on this, too.
I never quite got to understanding the people insisting the system was relatively cheap to produce. For one it needs "higher grade" silicon for the GPU clocks, then there are the costs associated with Tempest Engine and the I/O block hardware, not just in terms of R&D but also the actual BOM costs those will chomp into the budget (even if ultimately money is saved by handling most of that production in-house on those components...at least I think that would be the case).
The BOM itself may not push $600 but if you then consider the associated costs of assembly, QA testing, and marketing broken down per-unit I can see the associative costs hitting near it. Especially once you consider the controller and the features it will have, and the level of quality I'm sure they'd want to achieve with them (i.e don't go putting no cheap-ass mic into that controller!).
Another reason I think he might be right is because the Series S, IMHO, is definitely at a higher BOM relative the retail price, and that system is only providing less than half the graphical performance of PS5 and with both a smaller and slower SSD, more "basic" controller etc. Yet rumors suggest MS are taking a bigger loss on that than even Series X, so the idea Series S BOM could be closer to $350-$400 is possible, then, again, you have to factor in assembly costs and the such. I'd say Series X's BOM is probably either close to $500 or just very slightly north of it, then with the aforementioned assembly, marketing etc. costs per unit it's likely $600 for total production costs or a little north of that.
FWIW I don't think PS5 Digital removing the Blu-Ray disc drive brings BOM prices down much at all; the disc drive would only cost Sony probably $15, maybe $20, since I imagine they could manufacture it themselves plus they wouldn't need to pay the royalty fee (why would they when it is a technology they helped create?)