Exactly, wealth is being concentrated at the top to such extremes that there is no more excess money in the lower/middle classes to tap. So somehow or other the increase in wages will have to come from the wealthy, whether through intentional redistribution, market forces, or peasant uprisings. Likely some combination of all three.

Eventually it just becomes a physics problem. If $100 exist in the world, and one guy has $99, and you need to fund something that takes $2, you have to get $1 out of the rich guy somehow.