The reason whole rads are worth more is that its easier to break the parts down in a furnace. Since aluminum
melts at a much lower temp it'll seperate from the copper in a furnace easier than it would be to process
a bunch of thin sheets of fins. Pop cans just get crushed and turned into a block that can be melted down.
You just have to look at time vs. Money. How long and how many more tools and consumables are involved in
breaking down rads