Herbert probably would have gotten killed at work even if his father had not made a wish for two hundred pounds, or for any amount of money. However, there is a strong connection between the monkey's paw and Herbert's death. The family stays up later than usual because they are entertaining Sergeant-Major Morris. The author drops a few indications that the three men were drinking a lot of whiskey and that they stayed up late. For example:
...the door closed behind their guest, just in time for him to catch the last train...
...nor prevent her from referring somewhat shortly to retired sergeant-majors of bibulous habits...
Morriss stays late, but the family stays up still later talking about the monkey's paw. So Herbert would have gone to work next day with a hangover and without having had his usual night's sleep. This would explain how he could have been groggy and inattentive and gotten caught in the machinery that killed him, and this would make it logical that Herbert would be the victim of the first wish. Since Mr. White had wished for two hundred pounds and Herbert's employers paid two hundred pounds compensation for his death, it was strong circumstantial evidence that the monkey's paw had somehow caused Herbert's death. But, on the other hand, it could have been pure coincidence.
Shortly before they receive their visitor from Maw and Meggins, Mr. White tells his wife:
"Morris said the things happened so naturally...that you might if you so wished attribute it to coincidence."