redgarl :
As for Navi, the goal is creating a GPU able to render 4k@60Hz for the consoles. We know that PS5 is going to be around 500-600$ giving us a good look at what Navi is going to cost, which is at max half of the console price.
First off, Sony is just buying APU dies from AMD, not full discrete graphics cards, so I don't think the prices are directly comparable (you can't even really separate the cost of the GPU and CPU for consoles). More importantly, they could easily design the console GPU to have a lower CU count compared to the full fledged desktop card to lower the cost for consoles.
As far as the next gen consoles doing consistent (real) 4K/60 FPS, without any major shortcuts or sacrifices to visual fidelity compared to normal PC 4K gaming, I'll believe it when I see it. IIRC the PS4 Pro and XBox OneX were both hyped as 4K gaming machines, but then ended up using various tricks and sacrifices to get pseudo-4K like checkerbox rendering and upscaling and whatnot.
I'm not saying that half the price of a PS5 (so $200-$300 based on the numbers you gave) isn't a realistic guess for Navi, but that's more because that's about the price range of mainstream graphics cards. Which is what Navi is purportedly targeting IIRC.