For .357 Mag and cheap shooting, I usually use a 158 gr. LSWC and 6 gr. of Unique. You could back down on that, if you wish to conserve powder. At 6 gr, you could get 1,166.7 rounds out of 1 lb. of powder. At 5.4 gr., you can get 1296.3 rounds out of 1 lb. of powder, and at 5 gr., you can get 1400 even. That's $2.75/box if you have to buy everything except brass ($15/lb for powder, $15/1000 on primers, $25/1000 for bullets). If you cast your own bullets, I expect the price will vary depending on how much you have to spend on components. A different powder and/or charge will yield a different # of rounds/lb, which will affec the calculation a little, as will buying in bulk.