Winning an auction is itself a warning sign that you paid too much
In any auction where bidders are individually guessing an uncertain true value, the winner is typically whoever overestimated it by the widest margin, not whoever valued it most accurately. Economists first documented this "winner's curse" in 1970s studies of oil companies bidding for offshore drilling leases, many of which turned out far less profitable than their winning bids implied. The fix, sophisticated bidders learned, is to deliberately shade your bid below your own best estimate.