The 1/6 Stater coin is about 2,700 years old. This old coin was only stamped on the one side. Originating out of Lydia, known as part of Western Turkey, this could be the oldest coin found to date. It's in the main exhibit in the Department of Coins and Medals of the British Museum. This coin was made with electrum, an alloy of gold and silver. It is believed to be from the dynasty of the Lydian king, the roaring lion Alyattes (about 610 - 560 BC) or perhaps his predecessor Sadyattes could be behind the royal blood line.
As much as I looked for the price of something like this, nothing has turned up, I'm guessing it could be priceless.
See the coin that sold for the most here.
The three legged buffalo here