Substitution. What materials you use to build something is a function of their property's and their costs. AKA, you can use timber frame or steel to build a house which one you chose depends on their costs not just their inherent property's because either one will meet the same basic needs (strength, durability, toxicity, etc.)
Also, economy's are complex enough that there are a wide range of cost/benefit trade-offs going on. Electrically silver is a better conductor than copper which is better than Aluminum. While silver costs to much to be used for most wiring copper and aluminum tend to trade off based on weight strength issues. So, high tension power wires tend to use aluminum due to it's physical property's outweighing electrical issues after costs are taken into consideration.
Again this is just the size of the market in nominal value. AKA if the price drops to 1/2 and you sell 2.1 times as much the total market increased even if everyone's margins where squeezed.
Also, economy's are complex enough that there are a wide range of cost/benefit trade-offs going on. Electrically silver is a better conductor than copper which is better than Aluminum. While silver costs to much to be used for most wiring copper and aluminum tend to trade off based on weight strength issues. So, high tension power wires tend to use aluminum due to it's physical property's outweighing electrical issues after costs are taken into consideration.
Again this is just the size of the market in nominal value. AKA if the price drops to 1/2 and you sell 2.1 times as much the total market increased even if everyone's margins where squeezed.