I can't remember the exact date, but I think it was in the late 1990's or early 2000's that two 300G convertibles went through the B-J auction. One sold for $195K and the other for $205K as I recall.
25 years ago $200K was a lot more money than it is today thanks to inflation, and I haven't seen any G convertibles bring that kind of money since, so from that perspective, they have indeed depreciated. I remember thinking about possibly selling my G convertible shortly after seeing those prices to get a Ford GT that was sitting new in the showroom of the local dealership for $135K. Those 2005-2006 Ford GT's were recently bringing at least twice that much, meaning you could then cash in and go get the best G convert available with Hellcat money left over, but my guess is that very few of us are in this for the speculative monetary gains of the 'collector car' game, and just really like the cars for what they are, no matter what anyone else thinks about them. 'Crossrams, fins, and the top goes down' still does it for me. For the foreseeable future, my G ragtop is going nowhere. It is a bit disconcerting to admit/realize that the 'cool 25-30 year old early 60's' cars I sought out in the 80's and early 90's are now over 60 years old and probably look more like a Model A or even a Model T to some 'youngsters' in the hobby today who never saw any on the road in their childhood. In 1980, I had no interest in buying something from the 1920's, so I do get what is going on in the marketplace. There's nothing you can do about it except to keep enjoying what you have and being thankful that you have it.