I read an interesting post from CJ Wilson and his view about the CGT values which leads me to believe it is and isn't undervalued.
According to CJ, CGTs are basically separating into 2 categories: drivers' cars and museum pieces. Drivers' cars are your "bottom value" CGTs still hovering around $600-$700,000. Museum pieces are you examples hovering over a million dollars. CJ's opinion is that the drivers' cars aren't bad, but they are vehicles that are going to need maintenance work in coming years for new owners that goes beyond just engine-out service. For ex., I didn't know the system that lowers and raises the rear wing is prone to failure and requires a $4,000 service to fix; it costs extra for a technician to remove all the rear body work to get to said area. Over the years, there are just parts prone to wearing that require a lot of money to fix. On the other end, you have the museum pieces that have no miles and collect value. They're cars that deserve the be driven, but are much more mechanically sound due to sitting around and thus, will save their new owners thousands of dollars upfront.
He believes the best way is to find the grey area, and look for cars that have been driven & recently serviced. He's said that there is a difference between a used example & a new example; used cars tend to feel nicer to drive because they have been worn in. Of course, CJ's ultimate solution is also his way: buy 2 examples in both areas.