because .40 S&W is high and 357SIG is just extortion. .45 ACP and 9mm seem to be more reasonable.
I usually buy by the case off the web. (usually from Ammoman). 9mm has historically been the cheapest, and .45 the most expensive. I havent seen that change as of yet. .40 and 357SIG are usually about the same to a buck a box apart, and about in the middle of the 9mm and .45acp.
These are his prices right now for what I usually buy. (shipping is included in the price)
9mm NATO 124gr $239/1000
9mm Federal AE $199/1000
.40/357SIG Speer Lawman $269/1000
.45acp Speer Lawman $319/1000
I was buying the Federal 230 grain GI .45 (its marked FC 02 "match" on the brass) from him when he was selling it. Its been awhile and I dont remember exacly what I was paying for it,(it wasnt really cheap) but its hot stuff and accurate, and some of the best .45 I've seen in awhile.
I usually dont buy .45 as I reload most of my practice stuff in lead. Even lead has gone up considerably. From what I'm seeing price wise for just bullets, its now a little over double what I was paying about a year and a half ago for the same stuff.
I also load for 357SIG, but it has never really been worth it, mostly due to limited bullet selection, but also especially when you add your time to it, so I usually just buy it in bulk.
I dont shoot that much .40 to bother.
Right now, piecewise, the 9mm WWB at WalMart is about the cheapest, but not by much, and only because your picking it up and not paying shipping. For loaded put away ammo, I dont think its as good as the Federal or Speer, but its usually fine for blasting and brass.