Comment by consteval
There's a fixed supply of money (ish, the real life stuff money represents is actually scarce). If wealth disparity is great that means that less money is available for working people. You can't really gain a dollar here without losing a dollar there.
The problem here is working people ARE the economy. If they no longer have the power of consumption everything crumples. Of course it's a sliding scale, but even just a bit less consumerism can be catastrophic for some industries.
Money is just a proxy for time spent, so yes there is a fixed amount because we all have only so much time.
You can make gains by new technology(printing press vs handwritten), cutting quality(cheaper inputs/materials) or improving efficiency(work cell design).
Looking at it from a view of consumerism paints a bleak picture, if you look at if from a view of social stability without a functioning economy everyone will starve since the fertilizer, DEF fluid, John Deere tractor code and everything that ties all those together are so far spread out that is has become like a spider web facing a hurricane.