Brains

A man has a car wreck and they have to amputate his brain.So the nurse takes him to the brain transplant wearhouse.On one side of the shelves are lined with brains marked $500.00 each. On the other side the shelves are lined with brains marked $200.00 each.The brainless man asks why the price differece.The nurse points to the $200.00 brains and explains that these are female brains, so they've been used.