> I don't have any idea what most of these other things are

It's what a poor person would invests in. There is great truth in your comment. We are ignorant of opportunities available to those in higher classes. Tax tricks, off shore businesses, multi million dollar art collections. I have no idea how these things work but I guarantee you it helps wealthy people build more wealth through opportunities not available to the poor.

I'm not American so some of those things I don't know about because they just don't exist in the same way or I know them by different names.

You don't need to be rich to make reasonableness investment choices with your limited savings.

Tax tricks are less important or impactful if you are poor. However I agree that the tax system is not helping. Moving to a simple tax system would be good for everybody. Payroll taxes are regressive for example.

Most middle class people don't have off-shore accounts, and we are comparing the poor to the middle class, not to the super rich. The same goes for art collections.

Those are things that make the super-rich different form middle class, they don't prevent poor people from becoming more affluent.

> Most middle class people don't have off-shore accounts,

That's my point. Just like poor people don't have enough space in their apartments to store bulk goods. The cost of being poor is invariant to your wealth. It's asking the wrong question.

Buying in bulk is typically cheaper and can be of even more benefit if there is a sale by buying enough to last until the next sale.

Yes but when you have a small apartment living space you can't have months worth of food stored.

Taking short term opportunity of sales of singular items makes sense. I often buy meat depending on what's for sale, but not months worth.

Maybe once in a while you can buy bulk for dry-store items like pasta or rice.

That's the point though - richer people with larger houses and sufficient refrigeration space at least have the option to save money by buying in bulk. Then again, richer people need a way of signaling their wealth to others so will typically by more "premium" products, so the two effects largely cancel each other out (as it is, the stats certainly don't show that the rich spend absolutely less on food than the poor - but certainly a significantly lower % of their income).

Having to buy a larger house, a larger refrigerate, a larger transport vehicle to get the option to potentially buy in bulk. When in effect what they actually do, and data shows this, they buy to much perishables and then throw them away.

So I can buy that yes, there some potential places where this theory could potentially apply.

However, if you derive a social theory from these effects, I would like to see some evidence of this effect being really large.

Compare that with the land use situation I keep bringing up, we have prove and had it for a long time that density and walkability does massively reduce the living cost of poor. This was modled in detail for California for example:

This video shows the results of some modeling done for California by a famous urban planner: https://www.youtube.com/watch?v=fUtdFbK4YG4