You can get good deals in pet shops IF you know what you're looking at AND they don't! I got a sister to Joe's amel bloodred (best deal ever), but my next greatest conquest was for a beautifu bubblegum motley snow corn that was being sold as "an albino" for $30.00.
As a general rule, though, shows are the better places to bargain hunt. However, Curtis' caution about being educated BEFORE the show is well needed. I bought a bloodred female from a "reputable, big name dealer" at a show last year as a proven feeder. Well, the animal died two weeks later from starvation, having never eaten for me. Since corns will not die from just two weeks of not eating, it was clear to me that my hatchling had NEVER eaten, and was not what I had bought with promises. It took a great deal of carrying on be me (and a few well placed posts on the BOI), but I finally got my money back.
The very best way to get a "deal" is to find a reputable dealer you can trust, buy from him/her what you want, and then count the little extra expense as money well-spent. The time you'll save in worries, phone calls, and vet visits will more than make up the difference in price!