Admittedly i did forget to consider the fact that Nvidia is fabbed at Samsung. With that considered i think the cost of the GPUs will be pretty close.But they a lot cheaper
We know that wafers are cheaper (TSMC VS Samsung). I think the most accurate number we have is 30% cheaper. However we don't know if there are any custom agreements are in place.
AMD probably got a really nice deal, since CPUs, GPUs and consoles are being fabbed there.
There is also the fact that Nvidia are running GDDR6X, which will be costly for them.