[chillax]

Wrt $ amount (from the article):

"The stakes Henrich used in the game with the Machiguenga were not insubstantial—roughly equivalent to the few days’ wages they sometimes earned from episodic work with logging or oil companies." - Probably far from $100.

[vacri]

We don't know how much the American study used, though. The $100 is just an example amount mentioned in the article, not a reference.