All I can offer is an anecdote. I have a 2015 Mazda 3 (top trim level, with 34,000 miles on it.) Purchased 4.5 years ago with 8k on it for just under $20k. Well over a year ago, I started checking KBB.com values to either trade it in or sell it. Back then, trade was close to $12k, and private party was a bit over $13k. I've checked several times since then, and the price has basically grown and grown. As of today, it…
If you really want to see something insane, get a quote on Carvana. I have a 2018 Mazda3T Sedan with really low miles (thanks COVID) and they're offering me more than the MSRP when I bought it three years ago.
This is key, otherwise you should save your time, private sales are the way to go in the current market for higher milage vehicles