"Streetcorner Sales" joke

The kids filed back into class Monday morning. They were very excited. Their weekend assignment was to sell something, then give a talk on productive salesmanship.
Little Mary led off: "I sold girl scout cookies and I made $30," she said proudly, "My sales approach was to appeal to the customer's civil spirit and I credit that approach for my obvious success."
"Very good," said the teacher.
Little Sally was next: "I sold magazines," she said, "I made $45 and I explained to everyone that magazines would keep them abreast of current events."
"Very good, Sally," said the teacher.
Eventually, it was Little Johnny's turn.
Little Johnny walked to the front of the classroom and dumped a box full of cash on the teacher's desk."$2,467," he said.
"$2,467!" cried the teacher, "What in the world were you selling?" "Tooth brushes," said Little Johnny.
"Tooth brushes," echoed the teacher, "How could you possibly sell enough tooth brushes to make that much money?"
"I found the busiest corner in town," said Little Johnny, "I set up a Dip & Chip stand. I gave everybody who walked by a sample.
They all said the same thing. "Hey, this tastes like shit! "
Then I would say... " It is shit. Wanna buy a toothbrush?"