Helping a friend out with a P7 purchase. I guess I need a quick debrief on what determines the value of these things. I've seen them in perfect shape at pawn shops for $500, and at gun shows you see a $700 one on one table right next to a $1700 one on another. What is determining these values? I understand the mechanical differences between M8s and M13, is that what these prices reflect? Is one way more valuable than the other? Is one caliber more valuable than the other?