I found no silver in my first box of half dollars. I was disappointed to say the least. It didn't cost me anything but time so I really can't complain! I recorded myself going through the rolls but decided that would be too boring to watch so I just uploaded myself throwing back all the halves into a box. It was actually quite fun to put them all back. http://www.youtube.com/watch?v=whSwKPn_xEk
Cost you time and gas. Plenty of silver out there, my last two boxes have given up 3 90%'ers (1 '63 Frankie) and 9 40%'ers. Of course my previous 4 boxes had nothing, so it all balances out...