The sadder the story, the more valuable the toy. That is a human element and it's one that no painting has. The specific history of sorrow or joy in a child's life, when determining the price, means the sky's the limit.
-- Leo (The Under Graham Railroad Box Car Set)

Importance: Leo explains the value of toys to his friend, who is an art dealer. This is an indication of Leo's preoccupation with the stories associated with the toys he collects. When Leo cannot ascertain the story of the Under Graham train, the chain of events that resulted in it being in the Harts' possession, he becomes frustrated and obsessed. The train's story is its soul, and Leo's lack of knowledge on the subject is a metaphor for his lack of a soul.

...an innocent child paying for generations of stolen trains, stolen cars, stolen land, stolen horses, stolen history, stolen people arriving at a strange land inside a merchant...
-- Leo/Rev. Hart (The Under Graham Railroad Box Car Set)