Are you buying or selling? I got mine at scrap lead prices, but bought a tonne of lead at the time, then spent the next summer processing all the wheelweights and sorting through what I had.
I ended up with several different types of lead that I keep separate ( and labeled!!!)
I wouldn't melt it down into ingots, but leave it as is, so that you couldn't be accused of not selling what you say you have (like blended in a bunch of wheelweights to make the "good stuff" seem like it's more than actually there)
For me it'll end up as trading stock, but look at rotometals for a baseline as to what you might prices your stash at.