> Upper class society seems to still honor those implicit social contracts, but only if you are already part of the in crowd and your disfavor could come back to bite them.

And this is exactly how "barter and <<mutual aid.>>" worked "Before we reliably had money"; this is exactly "the implicit social contract behind such interactions" that you refer to.

Upper class society is a small group, pretty close to the point of everyone in it knowing each other. The average degree of separation[0] is going to be less than 2; I'd bet excluding a few outliers and wannabes[1], the maximum degree of separation will be 2. Meaning, if you're upper class, everyone else in upper class is either your acquaintance, or an acquaintance of your acquaintance. At that scale, the informal social mechanisms reign supreme. They may be influenced or channeled by the formal system of laws, but they're not replaced by it.

(Note that this isn't the "lowest" / most implicit level of group mechanics. Upper classes tend to have codes of conduct, etiquette, honor codes, etc. That's the consequence of size and weak binding of the group. The average degree of separation is still greater than 1, and even those you know directly, you may not hang around with much - so you need some structure to boost the implicit, informal social self-regulation mechanism. In a way, those upper classes sit at the intermediate point between early, small human tribes, and organized societies that came later.)

Conversely, if you're poor, you're in a huge social class, and your social interactions are dominated by those with total strangers. Average degree of separation is above 2, probably above 3. You're almost always dealing with strangers who themselves are also almost always dealing with strangers, and most of the time those dealings are effectively one-off - you have one interaction with a random person, and then neither of you are likely to ever cross paths again[2].

The point I'm getting at is that most people in the modern world have a large amount of one-off, transactional interactions with others. Such interactions are too brief and too weak to allow for bonds to form - and without that, there's little in terms of mutual obligations, or mutual care. What you get is the baseline "stranger treatment".

This is not to justify the conduct of people taking advantage of others, knowingly or not. I'm just saying that at this scale, all most of us can expect is the baseline "stranger treatment". Money isn't the direct cause here - the scale of our societies is. Money is merely what allows societies to scale this far, and it shouldn't be blamed for problems that are problems of scale.

As for the "common phenomenon of well-heeled individuals knowingly preying upon lower classes" - that is indeed a challenge, because at this scale, implicit social defenses (like people having reputation and getting shunned if it gets too bad) don't work. The options we have instead are more difficult to use and slow-acting - teaching people empathy, promoting a more benevolent culture, and adjusting laws to discourage bad behavior. It works well for many things, not quite well for others, and takes a lot of time to adjust - but again, consequences of scale.

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[0] - https://en.wikipedia.org/wiki/Six_degrees_of_separation

[1] - And geography. E.g. the upper class in Poland and in Germany may know each other well, but they might have few direct connections to upper class in e.g. South Korea. But that's just because they rarely deal with each other, and thus doesn't impact the thrust of my argument.

[2] - To this, too, there are degrees. Consider us here specifically - you and me. We're both aware of each other, crossed paths on HN many times over the years - but those interactions are infrequent and inconsequential enough that we aren't much more than strangers to each other. We may be nice to each other, and I do consider you wise, but we aren't really taking each other into account during our daily lives.