One opinion on a worthy topic ...
It's a question everyone has asked at one time or another, a question with many answers. Times used to be when something basically had two values.... a "buy" and a "sell" price.
And then came the wheeler-dealers, the off-price marketers, the road shows, reality-TV and the internet. Wholesale and retail merged to become re-sale.
Prices varied depending upon the level of the market you dealt in and the volume involved. The distinction between dealers and collectors blurred as one became the other.
Today, confidence is replaced with confusion while reality erodes knowledge. Buying or selling, you seldom know if you're given the best price. Research is important but trust is paramount.
The true worth of an item is exactly what someone else is willing to pay. Nothing more, nothing less.