Why are Superbirds worth so much?

how may have you seen in real life..... I have seen a few at carlisle....and a few in binghamton ny a few years ago.....

Just in my area I have seen:
1 orange auto 440 4
1 orange 4 speed 440 4
1 blue auto 440
1 dark blue auto on the column 440
1 green one, not sure of motor/trans

There are also a few Daytonas:
1 red auto 440
1 orange auto hemi

It is one thing to see them, another to see them drive by you- but I have never been in one.
It has always been my #1 car to own, but just my luck everyone else wants one.