Economy of scale: once you’ve figured out *how* to make something predictably and reliably, as you make more and more, the dominating cost becomes the materials and labor (not the equipment or the engineering). So the overall cost per unit comes down as more are manufactured. Think of how much engineering goes into making a smartphone, and how much it would cost if they only made a few hundred!!
The example I love to give is disc brake pads. Cars and fancier bicycles both use them, they are similar materials and obviously cars use much beefier pads, but they are much closer in price than in size, because there are way, way more cars than bicycles with disc brakes.
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