I just looked up info on the much desired 1969 Z28, and it was $458. over the BASE Camaro (6 cyl.). That made it a 16.8% bump for the option.
In todays $ it would be around $5,000. on the base SS/1, or around $36,000 ($40,000. SS/2).
They would sell a ton of them at that price.
You want more buy the COPO or ZL/1.