Musk developed what he called an "idiot index," which calculated how much more costly a finished product was than the cost of its basic materials. If a product had a high idiot index, its cost could be reduced significantly by devising more efficient manufacturing techniques. Rockets had an extremely high idiot index. Musk began calculating the cost of carbon fiber, metal, fuel, and other materials that went into them. The finished product, using the current manufacturing methods, cost at least fifty times more than that.

— In our words · Source: Elon Musk (Walter Isaacson)