Why does Nick think that Gatsby “paid a high price for living too long with a single dream”?
chapter 8 & 9 in The Great Gatsby
Nick narrates The Great Gatsby in Minnesota at the age of 32, two years after Gatsby's death, and at the same age at which Gatsby died. So, he's had time to reflect on Gatsby's dream and death--both of which were intensely focused on Daisy.
Daisy was the sole purpose of Gatsby's desires. Gatsby reinvented himself for her. He changed his name for her. He amassed wealth for her. He built a house next to her. He worshiped her green light. Her voice to him was full of money. He threw lavish parties for her. He tried to stop time for her. And, in the end, he risked his life for her: taking the blame for Myrtle's death. In a perverted sense, he was a kind of false Christ-figure for her: dying for her sin (or crime).
But, Nick has another view of Daisy. Nick casts Daisy in a different light because he obviously never loved and lost her. To Nick, Daisy is a kind of temptress, a "red herring," a "little fool." To Nick, she is characterized as a bad mother, a bad wife, a bad lover, a bad driver, and an irresponsible materialist who hides behind money.
So it is no wonder that Nick says that Gatsby "paid too high a price" (his life) for "a single dream" (Daisy). If, indeed, Daisy's voice was full of money, she wouldn't have been worth much more than one of those poorly bred puppies that Tom buys in Chapter 2.