Admit it... part of you wishes you'd thought of it.
And the other part of you realizes that stuff like this just makes the cost on everything else go up. Which really makes you mad and even more incredulous.
I would have looked for hidden cameras if I were that clerk... but then, I grew up with "Candid Camera" and this is exactly the kind of stunt they used to pull!
This, however, appears to be for real.