I found a small airplane table lamp with its original shade in a junk store for $6. At the time it would have been worth about $100. I expect it's worth a bit more now.
I once found a re-covered* table in a dumpster. I'm guessing the owner thought it was unattractive and replaced it with something from IKEA. "As is" it would retail for about $600-$800 in an antique store. I kept it and it's in my living room.
* a re-covered table is a table from the 18th century that was brought to America from Europe. The original top would have be salvaged for the wood and a pine drop-leaf top put on the original base. The base can be several hundred years old while the top will be about 100 years old.