I paid $130 or so for my GA-P35-DS3R, fairly premium mid-range Core2-era board.
I also bought a few DFI X48 boards, just because, but I never really used them much in my own rigs, I don't think. I still have one BNIB, even. Those were possibly more than $200.
I paid $110-130 range for my Asus B450-F ROG STRIX Gaming ATX board (new), as well as my Gigabyte B450 AORUS PRO WIFI ATX (new).
I really don't see much reason to pay more, although I could be convinced, if the board makers and chipset vendors could make a compelling price/performance or value/$ argument.
I'm doing great with a B450 board and my Ryzen R5 3600 and my RGB DDR4-3600 RAM... although I do average one serious freeze/crash every few weeks. Then again, I'm generally mining on my rig, which kind of pushes the limit on things. OTOH, I was doing a 5-day PrimeGrid race on the CPU, while mining on the GPU, and it never skipped a beat. So I don't quite know why my rig acts up once in a while.
for instance I would easily pay $249 for a fanless X570 board.
I would consider that. I've been willing to "stretch my (previous) budget limitations" with my Ryzen rigs, they offered enough performance and value, to consider "stepping up" into their price category, from the budget gear I used to use.