I'm not entirely convinced by the study that Henrich used for the Machiguenga people. It seems to rely heavily on the assumption that a choice to accept or punish remains relatively constant as the pile of cash gets larger. I'm a little skeptical of this, and I feel like as the stakes get higher, people are more likely to accept a lowball offer, because it still amounts to a sizeable chunk of cash. It mentioned that the money was equivalent to a few days wages for the Machiguenga, and I'm curious if it was the same amount (in time, not gross dollar amount) when they did the study in North America. And even then, there are plenty of other variables, like how desperate you are for money, how much you have in savings, etc. I suspect there are a lot of other factors at work here.