...when productions ends for them.....
Just like the Precision Miniatures 1:18 So-Cal Belly Tank Lakester LSR from some years ago.....
The market value for them quickly doubled when it was retired by the maker and all of the sudden, many collectors suddenly just have to find one for their collections.
But unfortunately, value and demand went back down when Replicarz decided to re-issue the car not so long ago.
It would not be different for this Bizzare Nardi Twin Boom LM racer, or most other models of "non-mainline" cars, I suspect.