Yeah. It's not a sunk cost, it's a continuation of the original probability.
How big of a loser am I tonight? I just got three cards and physically did the experiment. When I stuck with the original card, I won 11/30 times. When I switched cards I won 18/30 times.
(Play "The Maths Theme" from Eric's D&D adventure... the same one where Enron stood around in the hourglass for some reason....)
Anyway I've had enough math for now, so here are some random pictures from my picture folder.