Here's an example of an ultra rare muscle car and it' value.
1971 Plymouth "Hemi" Cuda convertible
Value in 2000: $49,600
Value today: $2 million
Source: Kelley Blue Book
(Photo may differ from the specific car named. Car pictured is 1970 model.) Introduced in 1970, there were few takers that could step up the plate with the extra cost for one of these powerhouses, add to that sky-rocketing insurance rates and production was just a few hundred. Making its final appearance in 1971, it is reported that a mere dozen 'Cuda convertibles were equipped with the Hemi, no two alike in color, trim and transmission choices
-Phil Skinner, KBB