I know pins are worth what you are willing to pay
In my opinion, if a pin "Sells" (key word is "sells") constantly for around the same price then you can pretty much say that is the value of the pin at that time. They must be actually selling for that price though not just what people are asking for it. Like I always say, I can put a dog turd on Ebay for $100, that doesn't mean it's going to sell.
Remember....pin prices will always come down in time. When "highly wanted" pins first come out prices always seem to go through the roof but in time the prices always comes down.