I'd wager that 1 out of 100 people with the bankroll to play 100k hands has the self discipline not to let emotion start affecting wager size/strategy.
That's (likely) what the casino's were hedging on, and in this case he obviously did.
I would also bet that their bet that emotion would come in pays off more times than not.
Hadn't ever heard of that though - 20% discount - unreal.