GG White book
1967 Dart GT 273-4 2645 produced
Hardtop/convertable 273-4/4 speed - 947 produced
No further breakdown between the hardtop and the convertable numbers
Fairly rare car
It's funny how every society is based around scarcity. The moment something is considered rare(scarce), everyone wants it, at least with things like precious metals such as gold or platinum.
In the car world however, just because there are only a few examples left does not necessarily make it valueable through scarcity. It has to be something somebody wants(desirable).
All it takes is that one person willing to pay what the owner wants, until that happens it's exact value is not really known. The owner of this convertible is hoping to score a large sum of money for a worn out rusty mess in hopes someone assigns a value to it based on it's scarcity.
While they have not found a way to spin gold from straw yet, they do know how to make diamonds which are almost indistinguishable from ones naturally occuring. This has an effect on the value of real diamonds when one can own a copy for a fraction of the price.
Same can be said of muscle cars, if you want a 273 4/4 convertible and don't want to pay the jeweler's ransom for it, you merely create one from a lesser optioned convertible and then enjoy the car as if it came that way. Miss Belvedere(google Tulsa, OK 57 Fury) is considered rare as it is the only time capsule 57 Fury known to exist but their is not a line of buyers trying to procure it. Yes, Tulsa buried a 57 Fury in a time capsule and then unearthed it a couple of years ago.
A car is a terrible investment as it will always need maintenance due to use and decay, plus it can be destroyed through a mishap. Starting with a sound chassis and body and building it up would be cheaper than buying a used up numbers matching car for big money and trying to rebody it anyway. Plus the money sunk into it will most likely be much higher than the value the market place will assign to it when you sell it.
A numbers matching hemi powered Daytona or Superbird is almost a no-brainer as long as the math adds up but most old car purchases are not like that.
Also, respectfully to the OP if you do not have a place to store it, the price is not really the issue. Best advice, do not allow your car collection to grow larger than your garage and always know when to walk away