Supply and demand... simple as that. Not just applicable to firearms but to everything else that's bought and sold in a "free market" economy.
I want an original 1968 or 1969 Camaro Z-28. Always regretted selling my 1968 Z-28 back in the day... but went off to play in the Army and had to get rid of it... bought it for @ $3k and sold it for $1,500
Today if I want one in good condition it's going to cost me well over $50,000
I don't wine about it... I simply have to decide if it's worth it to me. I don't fault the guy who has one and asks that price... what it originally sold for is not the issue... what I originally paid for mine when it was new is not the issue... it's worth whatever the current owners can get for them... that's the reality.
Are they overpriced? No... since they are finding buyers willing to pay that price. The market determines the value of something... asking price is not the point... average selling price indicates the true value as it represents what buyers are willing to pay and that will change all the time.
Mark