Like anything historic racing car, price of each individual car is dictated by it's history. That being said, the lotus 23 was an iconic sports racer of the era and nice examples (even without a rich history) command well into the $150k range.
About 30 years ago my father had the opportunity to buy one for $600. He told the guy he'd take it and instructed him not to sell it, rented a truck and trailer from his friend and drove from colorado to kansas to pick it up. When he got there the guy told him he sold it 2 hours ago. :banghead: