He was also able to negotiate good prices for the future harvest because the olive-press owners also wanted to avoid the possibility of a poor yield. When the harvest came, the olive yield was...

He was also able to negotiate good prices for the future harvest because the olive-press owners also wanted to avoid the possibility of a poor yield. When the harvest came, the olive yield was exceptionally good and this raised the demand for oil presses. Thales then sold his (futures) contracts of the olive presses and made a lot of money.