> the cost of building those unique shaped legos explodes with the size of the lego piece required.

The cost of plastic injection molding is almost entirely due to the cost of creating the steel mold. My argument is: with LLMs we are entering a world which makes it cost effective to build many more things from scratch, which is akin to going from building things out of pre-fabricated lego pieces to 3D printing (agreeably not cost effective for everything, but for many things).