The ending of this excellent story which I would avoid if you suffer from vertigo is incredibly ironic for a number of reasons. The most obvious irony lies in the fate of the yellow sheet of paper that Tom has risked so much to save. Having nearly killed himself to go and get it, Tom returns to his appartment and leaves it on the desk. However, as he opens the front door to go and meet his wife, warm air from the hall rushes through and blows the paper through the window that Tom had left open. Note how this is described and how Tom reacts:
As he saw the yellow paper, the pencil flying, scooped off the desk and, unimpeded by the glassless window, sail out into the night and out of his life. Tom Benecke burst into laughter and then closed the door behind him.
This behaviour is apparently contradictory, because Tom did everything he could to rescue this all-important piece of paper in the story. However, let us think about what this signifies. Having risked his very life for his work and his advancement by going out of his appartment and rescuing the paper, Tom has been forced to reassess his priorities in life. He has already decided to leave work and spend his time with his wife, and so when the paper "sails into the night and out of his life," this is symbolic of a decision Tom has already made: to focus less on work and more on the important things of life, such as his relationship with his wife. This is why Tom laughs at the end, because the loss of the paper cements a decision that he has already made.