Poorer people are happier. Alternatively, even when the aggregate or average level of happiness is not higher, some factors in it are higher, while other hugely negative factors (i.e. actually being poor) reduce the average or aggregate greatly.

The positive factors are strong social bonds.

Some people trade off the pursuit of money for living in areas with stronger and more generally dispersed social capital, with cultures of mutual self help, and spend more time on building their own social capital within it.

They're poorer financially, but wealthier socially.

But some people are poorer financially in areas where the social capital is generally poor as well, and particularly poor for the financially poor.

The problem is that middle-class people are trying to form friendships through just hanging out with people or trying to find common, shared interests. This is not strong bonds.

Can you imagine examples of how well-to-do people can put themselves into situations where they need to borrow items or services / help from their neighbors?

I think the problem is that wealthier people can buy the services they need, and so do so. Buying it doesn't impose a burden on your social equals, and so doesn't require taking on such burdens in a reciprocal fashion.

As you go up the wealth scale, for more and more things, you'd rather trade off money for time and effort, and you're able to buy that trade off from people who would rather have your money than their time.

This is apparent to all, people who make less than you, and people who make the same.

The people who make less will likely resent your requests for help, certainly if you haven't yet banked some help to them first, but even if you have, they're still likely to resent your trading off their time versus your money, knowing that you don't see it as worthwhile when it's your time vs. your money.

The people who make the same as you probably have the same time vs. money preferences as you do, would rather trade off their own money for their own time on their own problem, and so certainly won't want to be spending their time on your problem, when you obviously should just be spending your own money instead.

I think you're right that you get social bonding out of relations of reciprocating mutual aid, and also right that this gets harder to accomplish as you become more wealthy.

But I think you're wrong about the poor being necessarily happier, as you assumed that the reciprocating mutual aid would naturally occur if your'e poor. A lot of social and cultural capital that doesn't exist everywhere is required to make that happen.