IMHO, gunshow prices are “retail +” IOW “tourist pricing” for the rubes.
IF you and the vender are both IAA members, he may offer you a discount on a multi-piece purchase (but don’t expect it).
The lowest prices, esp on the “common” stuff is at a regular cartridge show (the first time you make the St Louis show you’ll be drooling all over yourself).
50 cal and under covers a lot of terratory, rimfire, patent ign, transitional types, BP loadings, US, British, Euro, military, sporting, wildcats, target, experimentals, etc are just some of the specialties in that size range.
As some general advise (and I’m passing on what I was advised to do when I started out) If you can locate a “general” collector in your area, perhaps he’ll be willing to allow you to view his collection. Select the type(s) that “turn your crank” and start a list of what cartridges you want the most (this helps to reduce the number of things to look at when you get to a real cartridge show).
Pick up reference books whenever possible, esp those that cover the area your most interested in. Cartridges of the World and Ammo Encyclopedia (both available from Dave at www.ammo-one.com ) make good “general/starter” references. More advanced references are things like the 4 volume set by George Hoyem, “30-06” by Chris Punnett (handy for a number of other cartridges also), the 2 volume (hopefully the 3rd volume will be out before long) set on US military small arms ammo by Hackley, Woodin and Scranton and John Barbers book on US/Canadian Rimfire cartridges. I don’t have any of Tony Williams books, but the reviews I’ve seen would qualify them as other ones to consider owning.
Purchase the “expensive” cartridges when you can (they only get more valuable) over buying a bag full of $1 cartridges (which will only ever be worth a buck).
Geeze, now it looks like “I’m” writing a book.