There are good and bad deals at gunshows. One must be educated FIRST and FOREMOST before considering buying anything at one. That said, I have yet to see an AR at a good price at a gunshow. I have; however, seen AR parts at excellent prices far lower than the gunstores I frequent. Also, even though ARs are more expensive at shows, I have seen many pistols, Glocks for example, that are up to $150 lower than the store will sell for. Magazines are typically far cheaper than gunstores as well.
Bottom line is you can find a deal or sure, but know what you are looking for and don't jump at the first table or even the first show. Be patient. These guys will get to know you over time and after you demonstrate you aren't a newbie, they begine to give you some good deals. Buy small at first as the more you buy the better deals you get later on.
Attend sundays in the afternoon...more often than not, there are better deals, especially if the show was slow on saturday. And, as already stated, don't discount the private sellers walking around. If a table buys it, they will turn around and sell it for 75 to 100 dollars more. Like I said, be educated and triple check what you are bying or you will get burned. Very few folks at the shows are watching out for you, but there are a few who do. After a few shows, you'll know who to buy from and who NOT to.