No two type of scrap from the same category can have the same price. For example, newspapers and books both fall under paper category but both have different resale value. Similarly, with Gold and any other metal, the value of gold will always be more. Let me give you a perspective why the scrap prices of different metal vary from each other.
Supply: There is plenty of iron ore supply than the demand in the market. Thus, the scrap buyers can buy iron ore in bulk at a very low rate. They not only buy in bulk but sell as well and that too with a good profit. But this not the case with copper or gold. The supply of copper is lower than iron ore so the price automatically goes up and when we compare copper to gold the price of gold is the highest as its supply is scarce.
Usefulness: Usefulness of a metal plays the most important role in the difference of price. Copper is a great conductor thus making it very useful in transmitting data and electricity. Though it is not available in bulk the price of scrap copper is lower than that of Gold which is also a good conductor but the availability is rare and it is very expensive in context to copper or even aluminium.
Recycling: Another important question one must ask while debating whether scrap metal prices should be equal or not is ‘How easily can it be recycled?’ For example, let’s compare steel and aluminium at this point. Aluminium can be recycled very easily and it can be sent back to a store shelf in just 60 days. Whereas on the other hand recycling steel take a longer time as the process is very complicated and has many steps. But there is way too much iron ore available easily making steel a slower recycled metal.
Yard’s ability: The scale of the scrap yard also determines the price of the scrap metals. The scrap buyers can buy scrap in bulk but if their yard does not can recycle that amount of scrap, the time taken to recycle the scrap in parts are way more than it can be anticipated. This subsequently increases the scrap metal prices. If a yard has the iron shredder but no copper granulator, then the prices of iron scrap will be lower than that of copper as for copper they would be using the more labour-intensive process which is expensive.
These are just a few reasons among many which can cause the fluctuate in the scrap metal prices.