Gur erny-jbeyq fgnxrf jrera'g gung uvtu (gra qbyynef), naq gur fpurqhyrq qhengvba bs gur rkcrevzrag jnf dhvgr ybat (gjb ubhef), fb V jnf jbaqrevat vs znlor gur tngrxrrcre cynlre ng fbzr cbvag qrpvqrq gung gurl unq n orggre jnl gb fcraq gurve gvzr va erny yvsr naq pbaprqrq qrsrng.
[TL;DR keywords in bold]
I find your hypothesis implausible: The game was not about the ten dollars, it was about a question that was highly important to AGI research, including the Gatekeeper players. If that was not enough reason for them to sit through 2 hours of playing, they would probably have anticipated that and not played, instead of publicly boasting that there's no way they would be convinced.
Update 2013-09-05.
I have since played two more AI box experiments after this one, winning both.
Update 2013-12-30:
I have lost two more AI box experiments, and won two more. Current Record is 3 Wins, 3 Losses.