There was once an old couple at a state fair. The man said to his wife, "Look dear, airplane rides are just ten dollars a piece. I haven't riden in a plane since the war. Let's do it."
But his wife looked at him and said, "Ten dollars is still ten dollars."
The next year at the fair the man said the same thing, and his wife replied, "$10 is $10."
This made the old man angry, so they got into a heated debate. The pilot of the plane overheard this, and walked over to them.
"I'll make a deal with you" he said. "I'll take you both in the plane for free, but neither of you can make a sound while we're up there, otherwise you both owe me $10."
The couple agreed to this arrangement, and soon they were in the plane. Of course the pilot, wanting to make his money, tried everything he could to make one of them scream. He went into a nose dive, turned the plane upside down, then went into a barrel role.
In the middle of this the old woman managed to fall out of the plane. When the pilot asked the old man why he didn't say anything to try and save his wife, he relied,"Ten dollars is ten dollars."