A lot of people who will sell guns will count on potential customers not knowing what a gun is worth. The typical prices and market values aren't as well known to most people. I went to a gun show recently, and one seller was offering up a P3AT for $460, even though I know they can be had for under $300, and in fact, 3 other sellers at the show were in fact offering them for less. Another guy was selling a Mosin Nagant 91/30 (not sniper) for $250, and they can be had for $80. It's kind of stupid at a gun show, because it's really very easy to compare prices, if you don't like a price, just walk 3 tables over, and see what a different seller is asking; but I can imagine outside of gun show settings, many people aren't willing to drive around all over town all day, or outside of their town, just trying to find the best deal and so some poor sap will pay far above market value.