$700 is actually probably a fair price for a PS5. You can't really build an equivalent PC for less than that. $900 to $1,200 would probably be close to how much manufacturing the PS5 Pro costs.
But PSN subsidizes these costs, which is why these systems can be this "affordable".
I doubt it costs that much. You're looking at it from buying PC components perspective. But they are mass producing identical boards with components that are 4+ years old by now, except the GPU. The cost of production is probably around the same as it was for non-Pro when it was released.
These days a good GPU costs almost $700 just by itself, mid range is almost $500, value is $400, budget is $250
The 4060 or the 7600xt are about in the ballpark for the original ps5, but you can't beat the price if you don't already have a computer with most of the components
900 to 1200’s an insane guess. This many years out R&D’s sure to have chilled out and companies that buy parts by the millions get them at much lower prices than individuals, plus partner companies that kit out their facilities to manufacture those parts recoup their investments in those facilities over time as well. I’m sure Sony’s still taking a few bucks hit on the sale of a console but it’s nowhere near close to double.