I've noticed that for a while (with many exceptions, of course, purely anecdotal), you can generally double your ram for the same price about every 3 to 5 years

I've noticed that for a while (with many exceptions, of course, purely anecdotal), you can generally double your ram for the same price about every 3 to 5 years. That's also about as often as you see process refinements leading to higher yield/surpluses along with newer models that benefit from process shrinks. Ram chip packages themselves have always been about the same size on the stick, so I figured it was a shrink that led to higher capacity for roughly the same amount of wafer used... so actual costs remained relatively consistent as it's the size cut from the wafer itself that tends to determine the costs for many things. Generally spitballing it here, but that would be my take on why prices have hovered around that $90 to $180 mark for two/four sticks of a decent capacity. I've had to budget about $200 for ram for nearly every build I've done in the past two decades.