"I am too big to climb and play," said the boy. "I want to buy things and have fun. I want some money." (36)
Personally, we hope we never get too big to climb and play, but we do understand that "wanting money" thing. This is the first time the boy seems dissatisfied with what he has—a perfectly good tree to climb—and is focused on obtaining something that's just out of his reach.
"I am too busy to climb trees," said the boy. "I want a house to keep me warm," he said. "I want a wife and I want children, and so I need a house." (41)
There's nothing unreasonable about the things the boy wants here, but the way he dismisses the tree when she asks him to spend some time with her is pretty rude. And the way he keeps repeating the words "I want" seems to indicate that he's dissatisfied with his current state of affairs.
"I am too old and sad to play," said the boy. "I want a boat that will take me far from here." (46)
There's no mistaking the dissatisfaction in these statements. Not only does the boy come right out and say he's old and sad, he also says he wants to sail away from everything. That's not an indicator of happiness and contentment.