My experience right now is that all sources of cheap lead that I used to have are gone.
You can see if you can buy scrap lead, but I think that they can't sell such toxic materials to "civilians." If you buy any, the current price is running about $0.47/lb., and I doubt it will come in ingots.
If you want to buy ingots already alloyed, you will be buying 1# ingots. These ingots are going for about $2. 1# is 7000 grains, so 1# will produce about 35 200-grain bullets. Thus, the alloy cost alone is $1/17.5 bullets, or $29/500 bullets (I think).
I can order excellent 200 gn .45 L-SWCs from mastercastbullets.com for $55.71/1000, or about $28/500.
Thus, I see casting as being much less interesting without a source of very inexpensive lead, and buying commercial bullets and melting them down may actually be cost effective.
I will be very interested if any one can give us a cheap source of lead.