Has an AFL game ever ended 73-21?
Exactly once. On May 2, 1903, Fitzroy beat Essendon 73-21, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 73-21 in league history.
That makes 73-21 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 74-21 has happened never and 73-22 has happened never.