There is fantasy value and actual value. I assume you are familiar with the Greater Fool Theory, where the price of an object is determined not by its intrinsic value, but rather by irrational beliefs and expectations of market participants.
To maximize the sale price one must find the last buyer in the ship of fools, so to speak.
For 1913 nickels, assuming provenance is provable, it is a trophy market for whales and sharks. Just try to take it to your neighborhood bank, store, or even coin dealer for immediate redemption. What is it really worth ? It's a sales game. For stamps and coins in general, Chinese entrepreneurs can make as many as the market demands, and there is a never ending war against sophisticated counterfeits and doctored coins. For stamps, there is decreasing demand due to technology and culture. In general, boys no longer collect stamps, or baseball cards for that matter.
I am familiar with the concept of the Greater Fool Value, but just have never heard it called that. Some examples are the 16th century tulip bulb mania in the Netherlands and the Beanie Baby craze of the 1990s where people were paying thousands of dollars for “retired” Beanie Babies.
I guess I should have called it the free market value of the stamps.