its because a lot more were made,so they got name recognition....everybody knows what a Camaro is, few know a Firebird...

of course 'normally' a lesser number produced car 'should' be more valuable....and it may happen....eventually..the birds ARE going up as we speak...not sure how much Maros are going up, havent compared them lately, but the birds seem to be up about 35% from 4 , 5 yrs ago...