Why does Amir call his birthday gifts "blood money"?

I a sense there are two meanings behind his reference to
having the birthday gifts as blood money.    In the book
The Kite Runner,  Amir wants his fathers love and support.  He
knows that he is a disappointment to Baba.  He wries and reads his stories to his
father, but nothing he does demonstrates to him that his father accepts him for who he
is. 

The day of the kite tournament is a turning point in
the story.  Amir and Hassan attend the kite tournament in Kabul.  Amir for once
demonstrates aggression during the tournament and wins by cutting the other kite's
string.  As a result he wins the tournament. 

Baba finally
sees some hope that his son can stand up and be aggressive.  He showed he can be a
winner.  When he gives such magnificent presents to Amir, the boy knows that he got hem
because he had won.  He also recognizes that he is only appreciated by his father at
this moment in time because he did win.

The second reason
that it is blood money is because after the tournament Hassan had run for the kite.  He
ran into the alley and Assef and his friends accosted him.  Hassan would not give Assef
the kite which angered Assef.  As a result Assef raped Hassan while Amir hid behind a
wall evident of the events.  He was unable to stand up for Hassan.  As Hassan left he
still had the kite and gave it to Amir.  The blood from the rape that was shed by Hassan
was the other reason those gifts felt like blood
money.