It isn't.

At least ...

I don't know if you will consider it private or not." "Go on," urged Mr.Dassonville.
"I just came to ask you," Peter explained, "if you don't mind telling me, how you got rich ?" "But bless you, young man," exclaimed Mr.Dassonville, "I'm not rich." This for a beginning, was, on the face of it, disconcerting.

Peter looked about at the rows of books, at the thick, soft carpet and the leather-covered furniture, and at the rings on Mrs.Dassonville's hand.
If Mr.Dassonville were not rich, how then--unless---- "I beg your pardon, sir, but I thought--that is, everybody says you are the richest man in these parts." "As to that, well, perhaps, I have a little more money than my neighbours." Peter breathed relief.

The beautiful Mrs.Dassonville's rings were paid for, then.
"But as to being _rich_, why, when you come to a really rich man all I've got wouldn't be a pinch to him." Mr.Dassonville illustrated with his own thumb and fingers how little that would be.