My only thoughts on this are that the frontal impact standards limited alot of the stuff that was so popular from being imported. There are not as many hot cars manufactured as there were pre-95. Alot of the model lines got waterered down. Toyota killed the Supra, the celica and the MR2. All that is left is the Altezza and the Trueno/Levin.
Another thing to consider is the quality level of cars being imported has dropped considerably since the industry was deregulated and other global markets have opened up. The prices in japan have risen for alot of these cars and in most cases with the limited profit margins they are no longer viable to import.
Since the vehicles are light on the ground they hold their price a little better.