For the last 18 years, every toy show or convention I've done, there has ALWAYS been someone that has offered a stupid-low price on something.
Customer : "How much is that Skystriker?"
Me : "$50.00, it's complete with both parachutes."
Customer: "Will you take $10.00?"
Me: "Sorry, I can't do any less than $45.00"
Customer: "How about $15.00?"

Yep, got a few of those yesterday which are the most classic.
But I also got some people who literally told me off...and for no good reason.
Customer: "How much is the Wing 0 Gundam figure?
Me: "that one is not for sale as it's on display only (no price tag), but If you want I have other Gundams in the bin over there at 10 bucks each."
Customer: "Nah, I'm just looking around out of Nostalgia"
Me in my head: "Then why ask for the price in the first place dammit!"

Oh well...they'll be back.