This is what I see on PCPartpicker right now:
PCPartPicker Part List:
https://pcpartpicker.com/list/Pnghgt
CPU: AMD Ryzen 9 5900X 3.7 GHz 12-Core Processor ($478.99 @ Newegg)
Motherboard: MSI B550-A PRO ATX AM4 Motherboard ($109.00 @ B&H)
Total: $587.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2021-11-27 10:17 EST-0500
PCPartPicker Part List:
https://pcpartpicker.com/list/dNj8LP
CPU: Intel Core i7-12700K 3.6 GHz 12-Core Processor ($418.48 @ Newegg)
Motherboard: MSI PRO Z690-A DDR4 ATX LGA1700 Motherboard ($209.99 @ Newegg)
Total: $628.47
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2021-11-27 10:18 EST-0500
Not a great mobo comparison since the Z690 board has twice the m.2 slots and 2.5Gb LAN, but you get the idea. $40 more for the 12700k platform, double the m.2 slots, 2.5Gb LAN, iGPU, quicksync, PCIe 5 and
If we include platform costs and actual street prices, the 12700k vs the 5900x is a very competitive matchup. I'd have to give the edge to the 12700k though. I also think a more fair comparison might be with an x570 board that has better features (and is a better match for the 5900x). But if we do that then Ryzen loses its platform pricing advantage.