any old iron ?

Searching for prices online does tend to suggest that cast iron is not a sought-after metal in the scrapyard business. You might struggle to get a better offer. It reminds me of my experience of recycling bottles for deposit in California. Each bottle had a 5cent deposit, and to get the refund, you had to go to a certain trailer, in a certain supermarket car park, on a certain evening of the week. There, they would charge a fee of 50% for each deposit, so in effect you finished up with a refund of 2.5 cents per bottle. And they wondered why there were still bottles scattered around in the parks.