I have a theory, I don't know how accurate it is, but it makes sense to me.
I think it comes down to education. To the vast majority out there, Callaways are a 'tuner' car, done in the aftermarket. Cars like the 288GTO, L88, IROC, are all factory option cars. People just don't realize that RPO B2K WAS a factory option.
I ran into this showing my cars all the time. When I talked to people about them and explained the significance of the B2K option, almost every single one of them was surprised. They did not know about the RPO-aspect of the cars. One time, when I was showing my Speedster, I heard a guy tell his girlfriend 'Nah, that's just a Corvette with a body kit', and they walked on by. (Ok, granted, there WAS a fair amount of 'body kit' aspect to the Speedster, but they had no recognition of the history).
Keep showing those cars. Keep spreading the word. Callaway's have EVERYTHING needed to make for a high-dollar collector car. They're rare, they are powerful, they are beautifully constructed, and the B2K cars ARE factory options. What they don't have is recognition.
Just my two cents.
(P.S. Just don't show and talk about them too much until I can get another one.)