It all depends on the person and their approach.
Used to do a flea market once in a while. Did one near my parents, and had lots of cards. Not much action, lots of lookers but few buyers. Left to have a look around and left mom in charge. Showed her the two cards I wouldn't budge on price, and said any offer that wasn't silly was fine for all the others.
Came back in about 20 minutes. Mom hands me about $75 and says "go look at more stuff" when I asked why she pointed out the guys standing at the decorative towel display a couple booths away. Which was odd since few guys did much looking at decorative towels there. She said they were the next flock of vulture looking to take advantage of the old lady while her kid was away from the table. She got darn near full price on everything! And they seemed happy to pay it.
Best sale was the kid with a handful of change asking how many cards he could get from the commons box. Checked with his mom, and told him he could get as many as he could fit in both hands.(Didn't want to do that if she didn't want him getting a lot of cards to leave laying around) He did so well I threw in a couple nicer cards too. He managed maybe 200 cards, not at all bad for a kid around 6-8. Best 37 cent sale ever.
Steve B