For ATX form factor motherboards, the price difference is mostly a wash. If you need a Micro-ATX motherboard, the cheapest AMD option carries a $20 premium over Intel. Those looking to build compact Mini-ITX systems can expect even bigger price differences.
The site notes that the Asrock A320M-ITX should be the cheapest Mini-ITX option for the AMD platform, with a MSRP of $99. Unfortunately, this motherboard is nowhere to be found. The cheapest Mini-ITX board you can actually buy right now is the Asrock X570 Phantom Gaming ITX/TB3, at $240. That's roughly $140 more than the cheapest Mini-ITX options for the Intel platform.
So why are there no low-cost small form factor motherboards for AMD's Ryzen? ExtremeTech speculates it could be due to strong demand for these boards, which may be emptying retail store shelves quickly. Alternatively, it could also be due to the coronavirus pandemic:
There are basically two reasons why AMD boards might be running expensive. First, it’s possible that some coronavirus-related inventory issues have resulted in better Intel board availability than AMD availability. We only see real gaps in mATX and mini-ITX. If manufacturers have cut back on building boards that AMD buyers don’t choose all that often, it would explain the limited inventory and high prices.It will be interesting to see how this situation evolves over the coming months and years.