The parts are more expensive for the Camaro to a point unless you got a serious build like stage II but like the Buick it has always responded well with every modification.
Cam kit for the LS is about 700.00+
The FAST intakes unless you buy used are between 750-900+ have seen them used for 500 LS6 intakes go for around 300-350
Suspension parts compare evenly in my opinion between the two.
My biggest complaint with the Camaro is the factory 7.5 10 bolt rearend. Horsepower around the 375-400 hp mark is the killer on them. I know there are several that have had good luck with them but longevity is the key and I wish GM would have at least put a 8.5 or a 12 bolt in.
The automatic cars seem to have the better luck of them. I installed a Motive 4.10 set and girdle that has survived the last couple of years with 1.5 60' times.
Stock 4L60 doesn't last long around the 400hp mark. Maybe a handful of passes down the track. Mine has been rebuilt twice and I make around 370hp. I think they compare fairly evenly but I do feel that my Buick could be faster than the Camaro with the same dollar investment I have in the Camaro right now because of the parts expense difference.