also what years would give me the most bang for my buck as far as things to look for? I've seen them as low as $150, but I've also seen them near $400 and more. is it certain years that command better prices, or just the seller looking to make more money? one thing is for sure, I want original mint bags that are sealed, not sure where to begin and dont' want to get ripped off. is there any general rule like 2-3-4x face or something? thanks.