A bloke appears in the circus manager's office, offering a new act. The manager is not keen, "Not really interested, I have enough acts".

The bloke says, "But hear me out, I think you will like my act"

"OK, what do you do?"

The bloke tells him "I climb up to the top of the tent and jump down head first onto the floor".

"Hmm, well, that might be interesting. Can you give a demo?"

The bloke says, "Sure. But I want $200 for every time I do it".

The manager says, "OK, let's see it"

The man climbs up the rope ladder to the top, and jumps down head first. His head goes into the floor some distance, and he has to extract himself. He stands up and says "I'll have to charge $400 for every jump".

The manager, "But you just told me $200!"

"Yes", said the bloke, "but I've never tried it before, and didn't know it hurts so much"