The 3D variants will hold their value until something better for gaming comes along, which is likely the next gen X3D parts or Intel's next gen uArch. Now that we've seen a round of price cuts, a large reduction in DDR5 prices, and motherboard pricing come down now it going to be the best time to buy. Otherwise you might as well lock yourself in for waiting for next gen.
CPUs were hardly impacted during the chip shortage. If it were still going on today pricing would still look similar. We already have shortage pricing baked in to CPUs, GPUs, and motherboards. All still inflated.
No, with a 4090 the processor absolutely has a large impact at 4K, especially if you use any sort of RT. The X3D variants in particular will benefit certain games regardless of resolution as the additional cache allows you to get through certain bottlenecks.
I'd have to agree with the other poster. $1,600+ on a 4090 and you are complaining about spending $120 more on a CPU that'll net you 22% more gaming performance across the board. I don't know what your system specs are but if you don't have a top tier CPU you are leaving performance on the table. Might as well limit your 4090 to a 60-70% power budget because performance is going to be identical.