Why are Superbirds worth so much?

They are big, kind of goofy looking but they were built for speed and I think they had a drag coefficient roughly the same as a C5 Corvette. That by far out did any other car from the era and would give them a theoretical top speed of at least 170 mph with enough gearing and a stock hemi or 440. Would be a cool car to clone and do a restomod but only with an efi supercharged 440 or hemi and a nice 6 speed to really give it top speed potential..