The last line of the short story "One of These Days" reads: "It's the same damn thing." The mayor of the town says this in answer to a question that the dentist who has just pulled his tooth asks him. The dentist wants to know whether to send his bill to the mayor personally or to the town administration. The mayor's answer indicates that he completely controls the town, including its finances, and so where the dentist sends the bill is irrelevant; the mayor will pay it from money he has stolen or extorted from the townspeople.
There are several clues throughout the story insinuating that the mayor is a dishonest and corrupt man. First of all, the dentist does not want to help him. He is a poor unlicensed dentist, and it would be reasonable to assume that under most circumstances he needs work and would take any patient who appears. However, he refuses to pull the mayor's tooth until the mayor threatens to shoot him.
Secondly, before the mayor comes in, the dentist checks that his revolver is ready in the drawer where he keeps it. He is prepared to kill the mayor if the mayor attempts to kill him.
Finally, the dentist realizes that, when he pulls out the tooth without anesthetic, the mayor will suffer excruciating pain. After he has grasped the tooth with the forceps, he says, "Now you'll pay for our twenty dead men." The dentist knows that the mayor has been murdering people to consolidate his power, and he feels the pain that the mayor will suffer will be some small compensation for the grief he has given the townspeople.
We see, then, that the mayor is an evil man who has come to power through bloodshed and controls the town by force. That's why he is able to make the statement that billing him or the town amounts to the same thing.