Actually, I'm pretty sure the Cobra and GTO are very similar in weight. I think it goes to show how lame America has become as far as driving is concerned. A car like that can only be sold on a limited basis in a niche market, so it's too expensive. The people who have that kind of money to spend buy BMW's and Mercedes. The young people they need to get excited about the car can't afford it. So, it stays a low volume niche car. It is just a catch-22, vicious circle type thing.
What they need to do is bring it down to the Mustang and F-body level. Strip it down some, get rid of expensive luxury options, and have available a version of it for well under $25,000, keeping the same powertrain. Or, just bring back the rough-riding, creaky, poorly assembled, uncomfortable, cheaply made F-body plastic-mobiles to get back into the market segment.