I disagree a little with the first item. Copper has a higher conductivity than gold, so there isn't an advantage in electrical performance to use all gold cond

I disagree a little with the first item. Copper has a higher conductivity than gold, so there isn't an advantage in electrical performance to use all gold conductors. It's only used in specific portions of a circuit board that you want to prevent from oxidation. Even if gold was cheaper than copper, you wouldn't want to make your whole circuit with gold metal. Even on IC's, which don't use a lot of metal, they switched to copper traces for the performance benefits.