It upsets me that some people think just because something's old or unusual it's worth a lot of money. It might be if it is in virtually 'as new' condition, especially cosmetically, but all too frequently ask silly money for tatty, damaged or with missing parts, typically iron sights which are very expensive or unobtainable. As soon as the blueing deteriorates, stocks are cracked or water damaged etc: or parts missing the value plummets, depending on severity (Blue book of airguns). For example, older BSA and Webley rifles and pistols are almost always overvalued, although largely plentiful, also pcp's needing repair spring to mind. It almost always costs a lot more, in parts, time and refinishing services, than it would be to buy a good example. Being a sceptic, I believe this is to catch out the unwary and airgun ignorant who then might become disillusioned with the sport. 'Let the buyer beware' doesn't cut it for me but 'let the seller be honest' does, especially with distance selling and not ftf.
Also overpricing clutters up the threads and becomes tedious.