These aren't over-priced, they're under-appreciated!

But seriously, a genuine, postally used copy of this stamp is actually tough to find. Stallzer has a nice CTO, but it's not as desirable.
As for the cat value, Scott lists the catalogue value of all new issues as twice face value ... and Unitrade followed Scott's example. Unrealistic, I know, but it is a practice that pre-dates me.
Brian