This is a pretty good article but it ignores one very important factor: the amount of VRAM you get per slot is often just as important as the amount of compute that accompanies it. An RTX 5090 for instance, in the largest configuration, is 32GB. An RTX 6000 PRO is 96 GB. That means that in the same number of slots you'll be able to put 3x as much VRAM and that's a massive advantage. 4 RTX 4090's are way easier to administer than 12 5090s, the power consumption will be lower and due to less bus activity you will probably get (much) better overall performance.
One of these days someone will figure out a reliable way to transplant a 5090 GPU to a 64 or 96 GB remanufactured card and then NVidia will have to find an answer if the volumes are high enough. I don't know the ratio of 5090's sold into the gaming channel versus RTX 6000 PRO and other datacenter products but I would not be surprised if the 5090's still held the edge.