from what I've heard, the conversation goes a little something like this...
you: I'd like to test drive a passat and get my $50 gift certificate
dealer guy: are you interested in buying a car or do you just want the stamp?
you: head! stamp! now!
dealer guy: grumble grumble
you: give it
dealer guy: here you go !stamp!
and then you get your $free $fifty $bucks.