Give or take 04-05 GTP/Comp G loaded with every possible option would cost 28-30k (correct me if I am wrong) This price goes for many other cars in the same category as the Grand Prix depending on the make.
As cars include more standard features, inflation, and technology the price of new cars have increased.
Dont believe me? Look at this article. http://moneyland.time.com/2012/04/06...ars-this-year/
The only car similar to performance/mid-size sedan as the Grand Prix that GM makes under 40k since Pontiac is gone is the Regal GS Turbo with every option which costs $38.660. That is a nearly 10k increase.
Sadly with a not so good economy the average American wages are not keeping up with the price increases of new cars. Which has led to a huge market for used cars.
Here is an article Used Car Sales Rise as Buyers Shun New Cars - MSN Autos
So if Pontiac was still around and the Grand Prix was still being sold today keeping in mind the redesigns, standard equipment, technology, and options how much do you think it would cost?