Definitely second what the ladies above have said (of course, it ain't fun till I get to add my two cents...).
I feel, though others may not agree, that one can also be as 'rigid' with the price of something depending upon the condition an item is in. So, I'd be more likely to pay a buttload for something in impeccable condition, and would offer to sell something in that condition for a price that would mean it's not so open to price offers.
But if something is in not so good condition, my 'strictness' if you like, decreases as the condition does, as do my expectations of what I could get for, say a postcard that's beat up and in wide circulation/availability. Mind you, if it's rare enough and beat-up as hell, I'm still probably stupid - uh, I mean dedicated! - enough to pay a decent wad of dough.