With fake items, its hard to say. The people pricing usually don't know enough about the items to tell a fake from a genuine article, but when someone comes saying that the item is fake, and they should sell it for $5 instead of $50 - Well, how are they to know if you are being honest, or are you just trying to score a genuine article for $5?
Yes, it does bother me to find counterfeit/reproduction items priced as genuine, but all you can do is let it sit. If nobody buys it they will be forced to lower the price, or sit on it.
You're absolutely right, I'm sure people try to scam to get a deal all the time. But what I've done is educate them on what to look for and what makes it counterfeit without wanting it myself, just trying to educate. I even offered to volunteer my time and come in and help them separate the fakes so they could price the real ones accordingly. they weren't interested. They also don't know all the designer labels and many times you can get a fab deal on a real designer handbag if you do your homework! So I guess you have a point, leave the fakes to sit and maybe they'll get the hint!