I'd just check eBay in your area. Search for this Mac and then in Filters choose "Sold Items". This will give you the actual sold prices - just take an average of those and there is your good price.
In the UK you can fetch such a machine for as little as £1,100. So I expect in the U.S. it will be around $1,100 or less.
Like @Andrey84 says, use eBay to get a guide for recent selling prices.
I've just bought an M1 16" Pro, 16/512 for use around the house and paid £1100 for it. I've been watching prices for a few days. The ones with 32GB RAM and 1TB etc seem to be about £1500 or so.
Amazon also do refurbished ones which might be worth a look.