Most car radiators today are made from aluminum with plastic tanks so you'd need to remove the plastic tanks of the aluminum radiator before most scrap yards will accept it as aluminum.
Clean Scrap Aluminum at the local scrap yard here is going for 40 cents per lb so you might get $1.00 to $2.00 out of the scrap aluminum radiator.
If the radiator you have is brass and you remove the steel from the brass radiator then you might get $30.00 to $50.00 from the scrap brass radiator once it's cleaned of any steel.