You can do very simple comparisson actually to this gen.
March 2012 - HD 7870 (which is, more or less, what's in PS4) - 175W - $350
July 2019 - RX 5700 - 180W - $379
That would put PS5 at $399.
If there is some additional hadrware block for RT, that would be somewhat decent, though still pretty weak for proper transition to 4K.
That's why we need to put an end to 399 USD price for everything, everything already expensive and 350 USD price for GPU is not for mainstream GPU anymore but for low end, PS5 and Xbox Scarlet will targeted for mainstream with price standard at 499 USD which is the new entry for base console standard. And also there wont be additional block of RT i believe, because the tech implementation for RT will be different from Nvidia, AMD will be using a hybrid hardware and software RT solution . It means less additional RT block with more optimization on software level.