Home made Legos for my sons. Or, Minecraft stuff...
You nailed it. I’d bet lego peices must cost $100/lb
Not near the precision necessary for Lego. The tolerances are so tight it's almost unbelievable. Yeah, you could make brick-like things, but if you build anything of any significant size or complexity, you'd have to use glue to hold it together. Lego is actually pretty amazing stuff, which you'll recognise if you ever try to build anything with knock-off bricks.
Since 1963, Lego pieces have been manufactured from a strong, resilient plastic known as acrylonitrile butadiene styrene (ABS).[24] As of September 2008, the engineers use the NX CAD/CAM/CAE PLM software suite to model the elements. The software allows the parts to be optimised by way of mould flow and stress analysis. Prototype moulds are sometimes built before the design is committed to mass production. The ABS plastic is heated to 232 °C (450 °F) until at a dough-like consistency. It is then injected into the moulds at pressures between 25 and 150 tons, and takes approximately 15 seconds to cool. The moulds are permitted a tolerance of up to two micrometres, to ensure the bricks remain connected.[20] Human inspectors check the output of the moulds, to eliminate significant variations in colour or thickness. According to the Lego Group, about eighteen bricks out of every million fail to meet the standard required.[25] Lego factories recycle all but about 1 percent of their plastic waste from the manufacturing process. If the plastic cannot be re-used in Lego bricks, it is processed and sold on to industries that can make use of it.[26][27]