I held my nose and bought an RTX 5070 Ti for $100 over MSRP in January. The very next week the same model was up $200. It turns out that NVIDIA had been subsidizing retail graphics cards with its Open Pricing Program. Not the whole story, but it may help explain the relative flatness of the graph until the end of January.

The other part of it is that the MSRP already baked in a substantial increase from the previous generation. While RAM was near rock-bottom pricing when this hit, current-gen GPUs definitely were not.

A $1500 5800 only has 16GB which would be $250 if you compare it against the DDR6 graph on that page. Given that there's only 2 top tier GPU manufacturers at most, they were probably already not very BOM cost sensitive.

RAM is just part of the GPU bill of materials?

It might also be that NVIDIA is a natural monopoly, while memory manufacturers are a cartel...