The kind of legacy that Willy leaves Linda and his sons is very much shaped by the kind of life that he lived. Let us remember that Willy Loman died trying to achieve the American Dream, and in a very real sense, sacrificed his life to try and gain the promises that the American Dream tantalises us with. This is largely due to the fact that he continues to unquestioningly believe in the dream rather than adapt his thoughts and beliefs in response to pragmatic realities of life. The American Dream gives no room for its adherents to admit failure or weakness, and Willy's complete acceptance of the creed of the American Dream leads directly to his death, which ironically is based on the belief that the money he can gain through his insurance is of greater value than his continued existence.
The irony about Willy's death is therefore that he is a man that gave everything to his belief in the American Dream and as a result of this sacrifice kills himself to avoid having to stop believing in the creed and doctrine of the American Dream. Although he is able to gain money through his death, he fails to realise that his sons and wife would have infinitely prefered having their father and husband with them for longer, even if he was a failure.