True story about estate sales. Probably 25 years ago one of the biggest collectors of coin-op pieces in the country died out in N. California. Huge collection of old arcade pieces, cast iron turn of the century stuff, and file cabinets full of manuals, sales literature, and factory letters, a lot of it one of a kind.
Well, his kids flew in to deal with the estate. He was sitting on a house worth several million, and it sold instantly. With the money from the house plus his cash and stocks, the kids were suddenly rich. That was all they cared about, and they didn't have a clue that Dad's stupid collection of games were worth anything. They had to get the house emptied fast, so they held a garage sale. They lined up his collection in the driveway and started selling it for pennines on the dollar. All of the rare paper items--they went into a dumpster.
Fortunately, another collector found out what was happening and got there in time to save the paper and shut down the sale before too many pieces had wandered off, but every time you see one of those ads and think it's a waste of time, remember that .0001% of the time it could be the find of your life.