Never was much of a yard sale guy, but most of the first half of my life I was at an auction at least 3 days a week. They used to be the best gauge for the value of any item. Then auctions suddenly turned into retail sales, and many bidders would bid more than retail of a new item, for a beat up POS that had little useful life in it. Now they are mostly gone.
FleaBay, Offerup, Craigslist, and all of the other ways for a person to sell items made them, well, gone. Sellers adding that "buyers premium" also helped kill them off. Used to be the seller (owner of the goods being auctioned) ate that as an expense, when they passed it on to the buyers it quit being fun.
I miss them.