I think at this point, starting from scratch and going all in, a new build is going to cost a lot for anybody. Sure you can get your feet wet with the older board and miss out on some of the newer features for less, and wait things out until prices drop, but that strategy only helps those who have the older parts on hand to swap over though. I did that when I upgraded from an old 2600K to a 4930K and then later upgraded various things (PSU, mem, drives, GPUs) on that rig (still in use btw with an EVGA GeForce RTX 3090 Ti FTW3 ULTRA ).
I did my first AMD build with the X570/3700K(used the wraith prism cooler which was impressive for a stock cooler) but reused some upgrades from the 2600K before it was retired (newer PSU and drives) and kept that price to just over $1K. I then upgraded it this past summer with the 5800X3D, essentially rebuilding it, to what it is now but if that had been done from scratch it would've been well over $1K.
On the plus side, both companies have offerings that allow a new build that could offer great performance for many years to come. I also appreciate how each is trying out new ideas and the highest clock is no longer a defining metric for gaming (although it's fun reading the records). AM5 is still in its infancy while DDR5 is maturing rapidly. PCIe 5.0, while not really needed, can potentially help out a bit with load times if all of the other hardware is able to take advantage of it but that means checking all the boxes to get there.
Meanwhile, there's the whole power issue. Why even bother to upgrade if not planning on upgrading to a new GPU? Regardless of brand, they are power-hungry monsters and a powerful CPU won't be able to strut its stuff without one. Between the CPU/GPU, most are looking at 1200W if wanting to be on the safe side, although less is certainly possible.
I was looking forward to a 13900K but now I think I'll wait and see what X3D offerings AMD has. In either case, I'm expecting to drop $1500-$2K for a new build that should get the job done for 5-10 years. It is a lot of money but I'm starting to put it away now and another reason I'm skipping this year's GPU releases. I've already read numerous rumors as to why NV has canceled, for now, a 4090 Ti or Titan, but I refuse to believe they won't release something 12+ months from now. There was a leaked image for the cooler today but I held off on posting about it because I'm already seeing takedown notices for it on other websites. Lol, it was only
900W.