For me, if I'm not buying imported, steel-cased ammo (Wolf, Brown Bear, Silver Bear), I get the best deals on brass-cased ammo at Walmart. Winchester "White Box" 1000 rounds of 9mm will run $113.40 before tax, and 45ACP will run $199.80 before taxes. In my neck of the woods, no one can come anywhere near the WWB prices at Walmart on 100 rounds of 38 spl, 9mm, 45ACP, and 380. I've seen other places advertise cheaper prices, but once I pay shipping costs for 1000 rounds of 45ACP, I'm better off just buying it from Wally World.
Interestingly, I just bought a reloader and am reloading 45ACP. I found out that Winchester vigin brass runs about $16 per 100 (I saw it for $23/100 on one site!) and Winchester primers are $20/1000 (or $2 per hundred). That ends up being $18+ per 100 just to have primed brass (no powder and no bullets). Throw in the cost of the bullets and powder, and you can't reproduce Winchester ammo with new Winchester components for the same price you can get them from Walmart. If I ever deplete my 45ACP brass, I'll buy more WWB 100-rnd packs just for the brass. Being able to shoot it will be an added bonus.