Most R&D today is geared towards datacenter, AI, research, etc. where AMD, Intel, Nvidia and whoever else jumps in can get 10X as much revenue per wafer. Desktop is merely a still significant sideline and a particularly convenient one when it can be used to monetize defects and surplus. Raising or maintaining mainstream prices despite reducing production costs is far more about passing more of the opportunity cost of offering mainstream parts instead of extra high-margin datacenter ones than any R&D costs.
This is the same reason why "mid-range" GPUs are getting stupidly expensive: every wafer wasted on chips for the unwashed masses is one less wafer available for highly profitable datacenter stuff. If people get complacent with prices going up all the time despite net costs going down, we'll be spending $1000 for "mid-range" CPUs and GPUs soon enough.