So for a similar launch price you get >2x the performance, almost identical pcie bandwidth (4x28) and faster memory (less of it though). Seems pretty great to me?
8x DDR4-2666 -> 2x DDR5-5600 is half the memory throughput too. That was the first thing that made my head scratch; having much bigger cores & still lots of PCIe throughput, but way less memory bandwidth.
That said, 8x DDR4-2666 also scaled up to 64c chips in Naples, this isn't unreasonable.
But you're comparing consumer/desktop to HEDT/server. They prioritize different things - the memory bandwidth is less of a bottleneck on desktop. While your premise is that the pricing is HEDT (based on a first generation part from 2017), the current Threadripper is a $6500 part that does still carry 8 memory channels, up to 3200Mhz.
One would imagine that EPYC based on Zen 4c would have the memory throughput you crave, though I wouldn't hold your breath for $700 pricing. It's still hard to say how committed AMD is to the middle ground of HEDT.
One thing to consider is the growth of cache. If you have better L3 hitrate (which you should given the doubling of L3 cache and 10x growth of L2 cache), you ease up the memory pressure a bit.
It's good that AMD doubled the lanes on the PCH as 4 was a real limit (some of the higher-end motherboards have 3xM.2s plus Wifi etc hanging off the PCH, so definately a bottleneck).
