I cast for handguns. Yes I use wheel weights. They are being phased out, don't know how much longer we will be able to get them. I have found them for free at times, but may have to pay. At present my son, who is a mechanic, keeps me supplied for free. You just have to look and see what you can find. Tire shops, mechanics, may have some around.
Cleaning them up has been pretty well covered.
"Is this economically a good thing?", you ask.
For sure it has been for me. I figure the bullets cost only 3 or 4 cents for the energy to melt the lead and the lube. (Not adding in the cost of the tools, and if you get free lead).
As scrap lead gets harder to find we may end up buying lead alloys from suppliers. I suppose we could still save some money doing that.