30 years ago I worked in a photo lab, where we recovered silver from the photoprocessing chemicals, which was then sold. Great little scam, since the IRS had no way of knowing how much silver the lab recovered. A service would come out, pick up the sludge and refine it into ingots. They'd also advise us when it was a good time to sell, or if we should hoard it.
Then one month the price of silver took a sharp rise. The service said hang on to the silver, it's going through the roof. Sure enough, it quadrupled in price in just a couple of weeks. So my coworkers started buying silver, too. My boss picked up $2k worth and asked me if I wanted to go halves on it, but my wife adamantly refused and I had to decline the offer.
Lucky for me, not so lucky for my boss. Turned out the price of silver had been artificially inflated when the Hunt brothers tried to corner the market. Once their scam was blown, the price of silver plummeted and never recovered. My boss - and good friend - hung onto that silver for the next 30 years. He died last year, never having seen those ingots ever be worth $2k again.