People go to garage sales and estate sales all the time.  Some get really lucky.  Here's a few stories of people who had something they thought was worthless but turned out to be worth millions of dollars.

A British farmer lost a hammer in one of his fields one day. Rather than going to spend a few bucks to just buy a new one, the man borrowed a metal detector and set out to find his hammer. Instead, he found something much more valuable. What he unearthed was a cache of Roman Empire era artifacts. To be exact, 15,000 coins of various metals, including gold, as well as jewelry and statues were all uncovered.

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From the Upcoming ueue, submitted by sish2000.