The best example I can highlight.
Before the WP myth tomes change, I used to make millions of gil off that place. Most people just didn't care about the chests, so after they'd leave, I'd go tag them. I was selling the sword from the chest in the square room for as high as 60k. The SCH and Bard items also sold really well.
Minutes, literally, before the servers came back online after that update, my PSU fried, and I was offline for two weeks. I came back figuring I could probably still get 5000 gil out of the sword, and a few thousand for the others.
Every one of them was under 100 gil. At that point, the only reason to list them is generosity.