It depends on what vendors are there, and you can also bargain with them. I just bought a 40 gallon breeder sized reptile cage (the kind with a screen top and doors on front). The retail price is around $150 and the guy wanted to sell it for $80 because one of the doors was broken (easily fixable). I bargained with him for a few minutes and got it down to $65. Last year there was someone selling reptile glass cages for a really great price but I haven't seen them at a repticon since, but there was a guy selling used aquariums at the last one in tampa i went to.
We like to get the VIP tickets and go super early on the first day. Although one we went to later on the second day and we found some great deals too. Either way just make sure you shop around and don't be afraid to talk them down on their prices.