LOL... I'm Jewish, so I guess it's in my blood.
I think as long as you're not making an insulting offer, the show vendors are usually willing to budge. Offering $50 for an albino retic will get you slapped, but asking "is that the lowest you can go?" on their original price is usually worth a shot. That's actually a good way to start the conversation, since it allows them to open the bidding (so to speak) - and also tells you quickly if they're willing to bargain.