Charley is refering to the theme of dreams and their importance in this play. The truth is that if we examine the play carefully, Willy certainly had lots of different other options in terms of how he could have spent his life. If he had been honest enough about his talents and abilities he could have had a very happy life working as a carpenter or a tradesman out West somewhere, as Biff realises. He also could have accepted a job from Charley, which Charley tries to offer him numerous times during the course of the play. What prevents Willy from accepting any of these alternatives is the American Dream and his own dream of gaining wealth, success and status from his profession.
Charley makes his comment in the Requiem after Linda makes the following observation:
I can't understand it. At this time especially. First time in thirty-five years we were just about free and clear. He only needed a little salary. He was even finished with the dentist.
Charley's comment therefore clearly establishes the fascination that men have with dreams and how hard it would be for any man to settle for a "little salary" when their dreams insist that they have a big job with a big salary. Perhaps his comment relates to man's pride and how we want to make our mark on the world. Charley's remark therefore encapsulates the dominance of the American Dream and the tragic consequences that can occur when it takes over somebody's life.