Htsthbjig's point is that if the money doesn't mean much to you anyway, you're more likely to be punishing because you're not losing much. But if it means a lot to you, why punish a stranger when you're getting a significant amount of free money.
To properly compare the cultural differences in the test, it would have to be done with the same level of purchasing power. That's not really stated one way or the other in the article. $100 goes a lot further in a developing country than a developed country, so if they were using the same dollar amount (I doubt they were), then it isn't a directly comparable study.
For example: Make it $10. The stranger gives me a 1:9 split in their favour. Fuck 'em, I'm not going to lose any sleep over a dollar, and it's not worth my time to even collect the dollar. Now make it $10k. Hey, I could actually do something nice with $1k, even if the other person is being 'unfair'. The relative purchasing power of the money in the test is significant within cultures, let alone across cultures.
I have no problem with the question "Have they considered purchasing power". I could also come up with a dozen possible issues they might not have taken into consideration. But I would never argue that they havent considered them before I actually checked. And even though it seems reasonable to say
"The relative purchasing power of the money in the test is significant within cultures, let alone across cultures."
I am not convinced that is correct. A quote from the paper describing the study [1] suggest that the amount of money is not crucial
"Indeed, in the UG, raising the stakes to quite high levels (e.g., three months’ income) does not substantially alter the basic results. In fact, at high stakes, proposers tend to offer a little more, and responders remain willing to reject offers that represent small fractions of the pie (e.g., 20%) even when the pie is large (e.g., $400 in the United States). Similarly, the results do not appear to be due to a lack of familiarity with the experimental context. Subjects often do not change their behavior in any systematic way when they participate in several replications of the identical experiment."
The point of the article is that it is the norm to conduct studies where participants are selected from the same non-representative sub-population, and that this methodology is heavily biased. Rejecting this idea, because you find a possible issue with one of the many studies it is based on, seems like a really bad idea.
20% of $400 is still not all that much unless you're in abject poverty. For a minimum-wage worker in the US, it's a little over a day's work, but for anyone else, it's vanishingly smaller. For a person on a median income (around $27.5k in the US), it's only several hours work. For a higher-level professional, it's not even an hour's work. $80 doesn't buy you a lot of professional time.
$400 certainly isn't three months income in the US (~$6900/qtr is the median), as suggested earlier in the paragraph, let alone the 20% split of that.
"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.
To properly compare the cultural differences in the test, it would have to be done with the same level of purchasing power. That's not really stated one way or the other in the article. $100 goes a lot further in a developing country than a developed country, so if they were using the same dollar amount (I doubt they were), then it isn't a directly comparable study.
For example: Make it $10. The stranger gives me a 1:9 split in their favour. Fuck 'em, I'm not going to lose any sleep over a dollar, and it's not worth my time to even collect the dollar. Now make it $10k. Hey, I could actually do something nice with $1k, even if the other person is being 'unfair'. The relative purchasing power of the money in the test is significant within cultures, let alone across cultures.