That's a lot of smelting to get the junk out of it. There's going to be the steel clips, zinc and steel weights, rubber valve stems, grease, oil, etc. For the extra work you're going to have to put in, I'd offer about .25 cents a pound, or maybe a little more, since they're delivering them. Once you get it smelted, it will cast good bullets without adding anything else in, so in the long run it's well worth the money and effort.
I checked what the only scrap yard in my area that will buy lead was paying last week, and it was .55 cents a pound for "clean lead". Wheel weights aren't considered clean lead. In the trade, it's called "dirty lead", since it has steel mixed with it, and more and more zinc and steel weights, so it's about half that. The other scrap yard won't even let you on their property with lead, so I only had one point of reference in pricing.
I've been trading for reclaimed shot, which is really clean, and getting it for the equivalent of .55 cents a pound, since it's a known quantity as far as lead/antimony content. By the time I get it, it can be used for reloading shotgun shells or for casting bullets, which is why I'm giving them top money for it.
Hope this helps.
Fred