Silicon chips are made by slicing up wafers; in general, the fewer transistors a design needs, the smaller the area it needs, so the more chips you get out of a wafer, and the lower the cost per chip.
But there must be some limit to this. Maybe you can have a chip of one square millimeter area, but it seems unlikely that you could have a chip of one square micron area.
What is the minimum... To be specific, I'm not asking what is the minimum physically possible area, but what is the minimum area below which chips stop getting cheaper? The point at which you stop trying to shrink your design, because fewer transistors will no longer save money?
And has this remained roughly constant over the decades, or has it changed with iterations of process technology, and if so, in which direction?