Vets' Bills

A woman brings a limp duck into the vet's rooms. The vet pulls out his stethoscope and listens to the duck's chest for signs of life. He shakes his head and says, "I'm sorry but your duck is dead".
"Are you sure" she protests, "you haven't done any tests. Maybe the duck is in a coma".
The vet rolls his eyes and whistles. In comes a black Labrador and to the woman's amazement sniffs the duck from bottom to top, shakes his head and trots off. The vet then calls, "kitty-kitty" and the Tabby wanders in, jumps onto the examination table and sniffs the duck from beak to tail, meows softly once and quickly disappears.
Confidently the doctor says, "the duck is dead". He turns to his PC and types, prints and hands her an invoice.
"450 bucks!" she cries, "450 to just to tell me the duck is dead?"
The vet shrugs his shoulders and says, "if you'd taken my word for it the bill would be 30 bucks. But with the lab report and the cat scan - it all adds up".