It is not pointless. You asked if 9900K may save 8K, which most here understood as if 9900K can improve the rendering speed. It can/will for sure, but the amount of improvement will depend on which CPU you upgrade from and for which games.
The video I posted and I commented on shows just four games, which are not representative of the VR games neither of pancake games in general. They just represent slightly different takes, e.g. RoTR was optimized by/for AMD and it shows even on CPU side, SoTR was not optimized for AMD (maybe for Nvidia?), FarCry is clearly not optimized at all. Metro, I do not know.
The only interesting point in this benchmark is at certain resolution (which translates to fill rate/rasterization power) both CPUs are "fast enough" as the GPU takes already longer time than those CPU needs. It does not have to be true for all games, maybe flightsims do need more CPU power (or are badly optimized and fall into FarCry rank) and you will still see the improvement in VR as well.
The idea is that if the game can utilize the CPU power smartly (which IL2 or DCS do not seem to do) the rendering speed (refresh rate) will be determined by the GPU and at certain scene complexity and target resolution it becomes the bottleneck even if you use RTX 2080 Ti, and when it happens, the small difference in CPU performance will not matter, i.e. it will not matter whether you have 8700K or 9900K or even Ryzen 2700X.
I am curious about how @SweViver benchmarks turn out, once he got his 9900K, but it will also depend if he will run it with his "old" 1080 Ti or already got 2080 Ti.