It’s nothing like a vehicle, they don’t hold their value. Unless it’s a pristine classic.But it's just like a bike you put upgrades into it what you like not necessarily what another wants. But even soon as you buy it it's used.
Supply and demand, if something which was once widely available is no longer easily attained, the value goes up.
Look at old smith revolvers, Mosins, SKS, M1 garand etc. they are used, and old, and outdated, yet the price continues to climb. Look at FN Ps90 and the 5.7pistol value now vs when they where new. People are still buying them for higher than what was retail.
An item being used is not the only determining factor to its value.