What is a fair price for a used Mazda3 with low mileage?

I've been looking at Mazda3s for like three weeks now and honestly my head is spinning a bit. i live up in the Seattle area so everything is already marked up like crazy but I really need something reliable for my new commute starting in May. I'm specifically looking for a hatchback, probably a 2019 or 2020 since I like the redesign they did then. I found a couple with really low mileage, like under 25k miles, and the sellers are asking for $23,000 which feels kind of high to me.

I did some digging on KBB and Edmunds and they say the fair market value for a 2019 with that mileage should be closer to $19k or $20k tops but then I go on Facebook Marketplace or Craigslist and everyone is acting like these cars are made of gold. One guy told me that because it’s the Preferred trim and has the Bose speakers it’s worth the extra three grand but I’m just not sure if that’s actually the case or if he’s just trying to fleece me because the market is still weird and inventory is low. It makes the online tools feel totally useless because nobody is actually selling for those prices.

My budget is strictly $21,000 including taxes and fees if I can manage it because I'm trying to avoid a huge loan. I'm worried that if I pay $23k now and the market finally cools down next year I’m gonna be underwater on the loan immediately. But then again if I wait too long my old Civic is gonna give up the ghost and I’ll be stuck taking the bus to work which would add like two hours to my day. Plus I plan on using this for trips out to the mountains on weekends so I want something that feels solid and not beat up.

Is it worth paying a premium for a car that’s basically just sat in someone's garage for four years or should I just look for something with 60k miles and save the five grand? What is actually a fair price for a 2019-2021 Mazda3 with low miles right now in a high-cost area or am I just dreaming with my $21k budget?