Just because you have scored a large supply of lead from someone who unknowingly sold it cheap, does not mean there is a significant supply of lead still in circulation that is generally available for bullet casting and will not likely ever be so again... unless you are one who is given to wistful thinking.
I have scored nothing, and said nothing of the sort.
However, if you call around to your local salvage yards, you'll find that the price of lead is down. ...Aside from the spot price having dropped, as well. (China isn't using anywhere near as much as they were a few years ago, so there's excess on the international market, which impacts the overall lead market.)
I know it's not an option for some people, but I even have more than one local yard that will sell to the public. ("Take a look around and come find us if there's something you like.")
There's still plenty of lead flowing through salvage yards, that
isn't wheel weights.
For 'smalls' there's everything from lead pipes, to lead flashing, to lead plumbers joints, and more; and for 'large' items, there's everything from 5-ton crane counterweights, to 300 lb babbit bearing blocks, to 4,000 lb pallets of linotype, monotype, and other printing scrap.
It's still out there, it's just harder for some people to find a willing seller.
And, unfortunately, some yards do have "all or nothing" policies. Right now, there's over 20k lbs of linotype and monotype sitting in 48 gallon drums at one of my local yards. The operator, however, won't sell me anything unless I take it ALL. Not only do I not have that kind of cash available in the 'hobby' budget, but I can't store it, either.