Will be around +50% increase for me (under certain conditions), upgrading from a 7600X. And an even bigger increase, for many with CPUs older than 2 years - albeit the difference between 5800X3D and 9800X3D may for gaming perhaps not be that convincing to upgrade, I suppose.
Personally, I like the PCIe 5.0 connectivity. And I want to go 4K eventually - for which the X3D CPUs make not a difference currently. But technically possible, that with the next gen of GPUs, CPU will once again become a bottleneck. Like, as is now, running a current-gen GPU at 1080p, gives a lot of frames - but even the 4090 can not really do that many frames at 4K. Whereas next-gen GPUs may perhaps see more frames at 4K, where the demand on CPU involvement would increase as well, from what I understand. Also, multi-screen setup, currently up to 6000x1440 pixels, with second screen on the iGPU of the CPU.
That already goes into quite specific circumstances though. If I were to set up just a 1080p gaming rig, 5700X3D and modern GPU would be plenty, coming in at under $1,000 for the entire rig.