I am quite reluctantly into ‘that sort of thing’….determining how much something is worth. This is often tough.
Take a McCoy vase, for example. There they are in a wet, mildewy box out back in the TP. A pretty pale green. Go on a site and it will consistently be selling for $150. let’s say. Stuck on the bottom is a piece of masking tape with a price scribbled on (if you want something to last on an item for decades despite weather please use masking tape….just don’t do it around me! very hard to scrape off) of $1.00. Did my Aunt not know the value of the ‘real’ McCoy? She has enough of it that she liked it or thought it worthy for some reason.
On and on it goes, and it is a trap of sorts. You need to move the stuff, but you don’t want to give it away and lose the true value. True value being what people are willing to pay and you are willing to invest in time and mental/physical effort to obtain that true value.