In certain states in America we have a redemption program for certain things; for example, in those states if you find a soda can it's worth anywhere between $0.05 - $0.10 (USD), so you count how many cans you have and bring it to the recycling center.
Some recycling centers doesn't want to be bothered with figuring out if you're lying so they go by weight; which is better for us because now those huge cans are worth anywhere between $0.10 - $0.20 (USD).
A funny thing about recycling copper is that people goes around stealing that stuff from places to recycle it. Some of them was caught and was on the news.